dnt-wd2.txt   dnt-wd3.txt 
W3C W3C
Tracking Preference Expression (DNT) Tracking Preference Expression (DNT)
W3C Working Draft 13 March 2012 W3C Working Draft 02 October 2012
This version: This version:
http://www.w3.org/TR/2012/WD-tracking-dnt-20120313/ http://www.w3.org/TR/2012/WD-tracking-dnt-20121002/
Latest published version: Latest published version:
http://www.w3.org/TR/tracking-dnt/ http://www.w3.org/TR/tracking-dnt/
Latest editor's draft: Latest editor's draft:
http://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html http://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html
Previous version: Previous version:
http://www.w3.org/TR/2011/WD-tracking-dnt-20111114/ http://www.w3.org/TR/2012/WD-tracking-dnt-20120313/
Editors: Editors:
Roy T. Fielding, Adobe Roy T. Fielding, Adobe
David Singer, Apple David Singer, Apple
Copyright (c) 2011-2012 W3C(R) (MIT, ERCIM, Keio), All Rights Reserved. Copyright (c) 2012 W3C(R) (MIT, ERCIM, Keio), All Rights Reserved. W3C
W3C liability, trademark and document use rules apply. liability, trademark and document use rules apply.
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Abstract Abstract
This specification defines the technical mechanisms for expressing a This specification defines the technical mechanisms for expressing a
tracking preference via the DNT request header field in HTTP, via an HTML tracking preference via the DNT request header field in HTTP, via an HTML
DOM property readable by embedded scripts, and via properties accessible DOM property readable by embedded scripts, and via properties accessible
to various user agent plug-in or extension APIs. It also defines to various user agent plug-in or extension APIs. It also defines
mechanisms for sites to signal whether and how they honor this preference, mechanisms for sites to signal whether and how they honor this preference,
skipping to change at line 50 skipping to change at line 50
Status of This Document Status of This Document
This section describes the status of this document at the time of its This section describes the status of this document at the time of its
publication. Other documents may supersede this document. A list of publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report current W3C publications and the latest revision of this technical report
can be found in the W3C technical reports index at http://www.w3.org/TR/. can be found in the W3C technical reports index at http://www.w3.org/TR/.
This document is a snapshot of live discussions within the Tracking This document is a snapshot of live discussions within the Tracking
Protection Working Group. It does not yet capture all of our work. For Protection Working Group. It does not yet capture all of our work. For
example, we have issues that are [PENDING REVIEW] with complete text example, we have issues that are [PENDING REVIEW] with complete text
proposals that did not make it into this draft. Text in white is typically proposals that have not yet made it into this draft. Text in blue boxes
[CLOSED]: we have reached a consensus decision. Text in blue boxes presents multiple options the group is considering. Options included in
presents multiple options the group is considering. In some cases we are this draft should not be read as limitations on the potential outcome, but
close to agreement, and in others we have more to discuss. An issue rather simply as possible options that are currently under consideration
tracking system is available for recording raised, open, pending review, by the working group. Readers may review changes from the previous Working
closed, and postponed issues regarding this document. This draft, Draft. An issue tracking system is available for recording raised, open,
published 13 March 2012, is substantially different from and more complete pending review, closed, and postponed issues regarding this document.
than the First Public Working Draft.
We have not yet reviewed comments from the Community Group associated with
this work. We thank them for their time and detailed feedback, and will
address their comments in the near future.
This document was published by the Tracking Protection Working Group as a This document was published by the Tracking Protection Working Group as a
Working Draft. This document is intended to become a W3C Recommendation. Working Draft. This document is intended to become a W3C Recommendation.
If you wish to make comments regarding this document, please send them to If you wish to make comments regarding this document, please send them to
public-tracking@w3.org (subscribe, archives). All feedback is welcome. public-tracking@w3.org (subscribe, archives). All feedback is welcome.
Publication as a Working Draft does not imply endorsement by the W3C Publication as a Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or Membership. This is a draft document and may be updated, replaced or
obsoleted by other documents at any time. It is inappropriate to cite this obsoleted by other documents at any time. It is inappropriate to cite this
document as other than work in progress. document as other than work in progress.
skipping to change at line 93 skipping to change at line 88
* 1. Introduction * 1. Introduction
* 2. Notational Conventions * 2. Notational Conventions
* 2.1 Requirements * 2.1 Requirements
* 2.2 Formal Syntax * 2.2 Formal Syntax
* 2.3 Terminology * 2.3 Terminology
* 3. Determining User Preference * 3. Determining User Preference
* 4. Expressing a Tracking Preference * 4. Expressing a Tracking Preference
* 4.1 Expression Format * 4.1 Expression Format
* 4.2 DNT Header Field for HTTP Requests * 4.2 DNT Header Field for HTTP Requests
* 4.3 JavaScript API to Detect Preference * 4.3 JavaScript API to Detect Preference
* 4.3.1 Interface
* 4.3.2 Attributes
* 4.3.3 Implements
* 4.4 Plug-In APIs * 4.4 Plug-In APIs
* 4.5 Tracking Preference Expressed in Other Protocols * 4.5 Tracking Preference Expressed in Other Protocols
* 5. Communicating a Tracking Status * 5. Communicating a Tracking Status
* 5.1 Tracking Status Resource * 5.1 Overview
* 5.1.1 Resource Definition * 5.2 Tracking Status Value
* 5.1.2 Tracking Status Representation * 5.3 Tracking Status Qualifier Values
* 5.1.3 Using the Tracking Status * 5.4 Tk Header Field for HTTP Responses
* 5.1.4 Tracking Status Caching * 5.4.1 Definition
* 5.1.5 Tracking Status ABNF * 5.4.2 Referring to a Request-specific Tracking Status
* 5.2 Tk Header Field for HTTP Responses Resource
* 5.2.1 Motivation * 5.4.3 Indicating an Interactive Status Change
* 5.2.2 Tk ABNF * 5.5 Tracking Status Resource
* 5.2.3 Tk Semantics * 5.5.1 Site-wide Tracking Status
* 5.2.4 More Information * 5.5.2 Request-specific Tracking Status
* 5.2.5 Implementation and Usage Considerations * 5.5.3 Representation
* 5.2.6 Examples * 5.5.4 Status Checks are Not Tracked
* 5.3 Status Code for Tracking Required * 5.5.5 Caching
* 6. Site-specific Exceptions * 5.6 Status Code for Tracking Required
* 5.7 Using the Tracking Status
* 5.7.1 Discovering Deployment
* 5.7.2 Preflight Checks
* 6. User-Granted Exceptions
* 6.1 Overview * 6.1 Overview
* 6.2 Motivating principles and use cases * 6.2 Motivating Principles and Use Cases
* 6.3 Exception model * 6.3 Exception model
* 6.3.1 Site pairs * 6.3.1 Introduction
* 6.3.2 Exception use by browsers * 6.3.2 Exception use by browsers
* 6.4 JavaScript API for site-specific exceptions * 6.4 JavaScript API for Site-specific Exceptions
* 6.4.1 Methods * 6.4.1 API to request site-specific exceptions
* 6.4.2 Methods * 6.4.2 API to Cancel a Site-specific Exception
* 6.5 User interface guidelines * 6.5 JavaScript API for Web-wide Exceptions
* 6.6 Exceptions without a DNT header * 6.5.1 API to Request a Web-wide Exception
* 6.7 Web-wide exceptions * 6.5.2 API to cancel a web-wide exception
* 6.8 Fingerprinting * 6.6 Querying a host's exception status
* 6.7 Transfer of an exception to another third party
* 6.8 User interface guidelines
* 6.9 Exceptions without a DNT header
* 6.10 Fingerprinting
* A. Acknowledgements * A. Acknowledgements
* B. References * B. References
* B.1 Normative references * B.1 Normative references
* B.2 Informative references * B.2 Informative references
1. Introduction 1. Introduction
The World Wide Web (WWW, or Web) consists of millions of sites The World Wide Web (WWW, or Web) consists of millions of sites
interconnected through the use of hypertext. Hypertext provides a simple, interconnected through the use of hypertext. Hypertext provides a simple,
page-oriented view of a wide variety of information that can be traversed page-oriented view of a wide variety of information that can be traversed
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content without such targeted advertising or data collection need a content without such targeted advertising or data collection need a
mechanism to indicate those requirements to the user and allow them (or mechanism to indicate those requirements to the user and allow them (or
their user agent) to make an individual choice regarding exceptions. their user agent) to make an individual choice regarding exceptions.
This specification defines the HTTP request header field DNT for This specification defines the HTTP request header field DNT for
expressing a tracking preference on the Web, a well-known location (URI) expressing a tracking preference on the Web, a well-known location (URI)
for providing a machine-readable tracking status resource that describes a for providing a machine-readable tracking status resource that describes a
service's DNT compliance, the HTTP response header field Tk for resources service's DNT compliance, the HTTP response header field Tk for resources
to communicate their compliance or non-compliance with the user's to communicate their compliance or non-compliance with the user's
expressed preference, and JavaScript APIs for determining DNT status and expressed preference, and JavaScript APIs for determining DNT status and
requesting a site-specific exception. requesting a user-granted exception.
A companion document, [TRACKING-COMPLIANCE], more precisely defines the A companion document, [TRACKING-COMPLIANCE], more precisely defines the
terminology of tracking preferences, the scope of its applicability, and terminology of tracking preferences, the scope of its applicability, and
the requirements on compliant first-party and third-party participants the requirements on compliant first-party and third-party participants
when an indication of tracking preference is received. when an indication of tracking preference is received.
ISSUE-117: Terms: tracking v. cross-site tracking Issue 136: Resolve dependencies of the TPE on the compliance specification
The WG has not come to consensus regarding the definition of tracking and The WG has not come to consensus regarding the definition of tracking and
whether the scope of DNT includes all forms of user-identifying data the scope of DNT. As such, a site cannot actually say with any confidence
collection or just cross-site data collection/use. This issue will be whether or not it is tracking, let alone describe the finer details in a
resolved in the TCS document, though its resolution is a necessary tracking status resource. This issue will be resolved by progress on the
prerequisite to understanding and correctly implementing the protocol TCS document, though its resolution is a necessary prerequisite to
defined by this document. understanding and correctly implementing the protocol defined by this
document.
2. Notational Conventions 2. Notational Conventions
2.1 Requirements 2.1 Requirements
The key words must, must not, required, should, should not, recommended, The key words MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
may, and optional in this specification are to be interpreted as described MAY, and OPTIONAL in this specification are to be interpreted as described
in [RFC2119]. in [RFC2119].
2.2 Formal Syntax 2.2 Formal Syntax
This specification uses Augmented Backus-Naur Form [ABNF] to define This specification uses Augmented Backus-Naur Form [ABNF] to define
network protocol syntax and WebIDL [WEBIDL] for defining scripting APIs. network protocol syntax and WebIDL [WEBIDL] for defining scripting APIs.
2.3 Terminology 2.3 Terminology
This specification uses the term user agent to refer to any of the various This specification uses the term user agent to refer to any of the various
client programs capable of initiating HTTP requests, including, but not client programs capable of initiating HTTP requests, including, but not
limited to, browsers, spiders (web-based robots), command-line tools, limited to, browsers, spiders (web-based robots), command-line tools,
native applications, and mobile apps [HTTP11]. native applications, and mobile apps [HTTP11].
The term permitted use is used to indicate a restricted set of conditions
under which tracking is allowed in spite of the user's DNT preference.
The term user-granted exception is used when the user has permitted
tracking by a given third party, usually in the form of a site-specific
exception.
A companion document, [TRACKING-COMPLIANCE], defines many of the terms
used here, notably 'party', 'first party', and 'third party'.
3. Determining User Preference 3. Determining User Preference
The goal of this protocol is to allow a user to express their personal The goal of this protocol is to allow a user to express their personal
preference regarding tracking to each server and web application that they preference regarding tracking to each server and web application that they
communicate with via HTTP, thereby allowing each service to either adjust communicate with via HTTP, thereby allowing each service to either adjust
their behavior to meet the user's expectations or reach a separate their behavior to meet the user's expectations or reach a separate
agreement with the user to satisfy all parties. agreement with the user to satisfy all parties.
Key to that notion of expression is that it must reflect the user's Key to that notion of expression is that it MUST reflect the user's
preference, not the preference of some institutional or network-imposed preference, not the choice of some vendor, institution, or network-imposed
mechanism outside the user's control. Although some controlled network mechanism outside the user's control. The basic principle is that a
environments, such as public access terminals or managed corporate tracking preference expression is only transmitted when it reflects a
intranets, might impose restrictions on the use or configuration of deliberate choice by the user. In the absence of user choice, there is no
installed user agents, such that a user might only have access to user tracking preference expressed.
agents with a predetermined preference enabled, the user is at least able
to choose whether to make use of those user agents. In contrast, if a user
brings their own Web-enabled device to a library or cafe with wireless
Internet access, the expectation will be that their chosen user agent and
personal preferences regarding Web site behavior will not be altered by
the network environment, aside from blanket limitations on what sites can
or cannot be accessed through that network.
The remainder of this specification defines the protocol in terms of A user agent MUST offer users a minimum of two alternative choices for a
whether a tracking preference is enabled or not enabled. We do not specify Do Not Track preference: unset or DNT:1. A user agent MAY offer a third
how that preference is enabled: each implementation is responsible for alternative choice: DNT:0.
determining the user experience by which this preference is enabled.
If the user's choice is DNT:1 or DNT:0, the tracking preference is
enabled; otherwise, the tracking preference is not enabled.
A user agent MUST have a default tracking preference of unset (not
enabled) unless a specific tracking preference is implied by the decision
to use that agent. For example, use of a general-purpose browser would not
imply a tracking preference when invoked normally as SuperFred, but might
imply a preference if invoked as SuperDoNotTrack or UltraPrivacyFred.
Likewise, a user agent extension or add-on MUST NOT alter the tracking
preference unless the act of installing and enabling that extension or
add-on is an explicit choice by the user for that tracking preference.
We do not specify how tracking preference choices are offered to the user
or how the preference is enabled: each implementation is responsible for
determining the user experience by which a tracking preference is enabled.
For example, a user might select a check-box in their user agent's For example, a user might select a check-box in their user agent's
configuration, install a plug-in or extension that is specifically configuration, install an extension or add-on that is specifically
designed to add a tracking preference expression, or make a choice for designed to add a tracking preference expression, or make a choice for
privacy that then implicitly includes a tracking preference (e.g., Privacy privacy that then implicitly includes a tracking preference (e.g., Privacy
settings: high). Likewise, a user might install or configure a proxy to settings: high). The user-agent might ask the user for their preference
add the expression to their own outgoing requests. For each of these during startup, perhaps on first use or after an update adds the tracking
cases, we say that a tracking preference is enabled. protection feature. Likewise, a user might install or configure a proxy to
add the expression to their own outgoing requests.
Although some controlled network environments, such as public access
terminals or managed corporate intranets, might impose restrictions on the
use or configuration of installed user agents, such that a user might only
have access to user agents with a predetermined preference enabled, the
user is at least able to choose whether to make use of those user agents.
In contrast, if a user brings their own Web-enabled device to a library or
cafe with wireless Internet access, the expectation will be that their
chosen user agent and personal preferences regarding Web site behavior
will not be altered by the network environment, aside from blanket
limitations on what resources can or cannot be accessed through that
network. Implementations of HTTP that are not under control of the user
MUST NOT generate or modify a tracking preference.
4. Expressing a Tracking Preference 4. Expressing a Tracking Preference
4.1 Expression Format 4.1 Expression Format
When a user has enabled a tracking preference, that preference needs to be When a user has enabled a tracking preference, that preference needs to be
expressed to all mechanisms that might perform or initiate tracking by expressed to all mechanisms that might perform or initiate tracking by
third parties, including sites that the user agent communicates with via third parties, including sites that the user agent communicates with via
HTTP, scripts that can extend behavior on pages, and plug-ins or HTTP, scripts that can extend behavior on pages, and plug-ins or
extensions that might be installed and activated for various media types. extensions that might be installed and activated for various media types.
When enabled, a tracking preference is expressed as either: When enabled, a tracking preference is expressed as either:
DNT meaning DNT meaning
1 This user prefers not to be tracked on the target 1 This user prefers not to be tracked on the target site.
site. 0 This user prefers to allow tracking on the target site.
0 This user prefers to allow tracking on the target
site.
If a tracking preference is not enabled, then no preference is expressed A user agent MUST NOT send a tracking preference expression if a tracking
by this protocol. This means that no expression is sent for each of the preference is not enabled. This means that no expression is sent for each
following cases: of the following cases:
* the user agent does not implement this protocol; or * the user agent does not implement this protocol;
* the user agent does implement the protocol, but the user does not wish * the user has not yet made a choice for a specific preference; or,
to indicate a preference at this time. * the user has chosen not to transmit a preference.
In the absence of regulatory, legal, or other requirements, servers may
In the absence of regulatory, legal, or other requirements, servers MAY
interpret the lack of an expressed tracking preference as they find most interpret the lack of an expressed tracking preference as they find most
appropriate for the given user, particularly when considered in light of appropriate for the given user, particularly when considered in light of
the user's privacy expectations and cultural circumstances. Likewise, the user's privacy expectations and cultural circumstances. Likewise,
servers might make use of other preference information outside the scope servers might make use of other preference information outside the scope
of this protocol, such as site-specific user preferences or third-party of this protocol, such as site-specific user preferences or third-party
registration services, to inform or adjust their behavior when no explicit registration services, to inform or adjust their behavior when no explicit
preference is expressed via this protocol. preference is expressed via this protocol.
ISSUE-111: Different DNT value to signify existence of site-specific
exception (also linked to 4.1 and 6 below)
4.2 DNT Header Field for HTTP Requests 4.2 DNT Header Field for HTTP Requests
The DNT header field is hereby defined as the means for expressing a The DNT header field is hereby defined as the means for expressing a
user's tracking preference via HTTP [HTTP11]. user's tracking preference via HTTP [HTTP11].
DNT-field-name = "DNT" ; case-insensitive DNT-field-name = "DNT" ; case-insensitive
DNT-field-value = ( "0" / "1" ) *DNT-extension ; case-sensitive DNT-field-value = ( "0" / "1" ) *DNT-extension ; case-sensitive
DNT-extension = %x21 / %x23-2B / %x2D-5B / %x5D-7E DNT-extension = %x21 / %x23-2B / %x2D-5B / %x5D-7E
; excludes CTL, SP, DQUOTE, comma, backslash ; excludes CTL, SP, DQUOTE, comma, backslash
A user agent must send the DNT header field on all HTTP requests if (and A user agent MUST send the DNT header field on all HTTP requests if (and
only if) a tracking preference is enabled. A user agent must not send the only if) a tracking preference is enabled. A user agent MUST NOT send the
DNT header field if a tracking preference is not enabled. DNT header field if a tracking preference is not enabled.
The DNT field-value sent by a user agent must begin with the numeric The DNT field-value sent by a user agent MUST begin with the numeric
character "1" (%x31) if a tracking preference is enabled, the preference character "1" (%x31) if a tracking preference is enabled, the preference
is for no tracking, and there is not a site-specific exception for the is for no tracking, and there is not a site-specific exception for the
origin server targeted by this request. origin server targeted by this request.
The DNT field-value sent by a user agent must begin with the numeric The DNT field-value sent by a user agent MUST begin with the numeric
character "0" (%x30) if a tracking preference is enabled and the character "0" (%x30) if a tracking preference is enabled and the
preference is to allow tracking in general or by specific exception for preference is to allow tracking in general or by specific exception for
the origin server targeted by this request. the origin server targeted by this request.
Example 1
GET /something/here HTTP/1.1 GET /something/here HTTP/1.1
Host: example.com Host: example.com
DNT: 1 DNT: 1
An HTTP intermediary must not add, delete, or modify the DNT header field An HTTP intermediary MUST NOT add, delete, or modify the DNT header field
in requests forwarded through that intermediary unless that intermediary in requests forwarded through that intermediary unless that intermediary
has been specifically installed or configured to do so by the user making has been specifically installed or configured to do so by the user making
the requests. For example, an Internet Service Provider must not inject the requests. For example, an Internet Service Provider MUST NOT inject
DNT: 1 on behalf of all of their users who have not selected a choice. DNT: 1 on behalf of all of their users who have not expressed a
preference.
The remainder of the DNT field-value after the initial character is The remainder of the DNT field-value after the initial character is
reserved for future extensions. User agents that do not implement such reserved for future extensions. User agents that do not implement such
extensions must not send DNT-extension characters in the DNT field-value. extensions MUST NOT send DNT-extension characters in the DNT field-value.
Servers that do not implement such extensions should ignore anything Servers that do not implement such extensions SHOULD ignore anything
beyond the first character. beyond the first character.
DNT extensions are to be interpreted as modifiers to the main preference DNT extensions are to be interpreted as modifiers to the main preference
expressed by the first digit, such that the main preference will be obeyed expressed by the first digit, such that the main preference will be obeyed
if the recipient does not understand the extension. Hence, a if the recipient does not understand the extension. Hence, a
DNT-field-value of "1xyz" can be thought of as do not track, but if you DNT-field-value of "1xyz" can be thought of as do not track, but if you
understand the refinements defined by x, y, or z, then adjust my understand the refinements defined by x, y, or z, then adjust my
preferences according to those refinements. DNT extensions can only be preferences according to those refinements. DNT extensions can only be
transmitted when a tracking preference is enabled. transmitted when a tracking preference is enabled.
The extension syntax is restricted to visible ASCII characters that can be The extension syntax is restricted to visible ASCII characters that can be
parsed as a single word in HTTP and safely embedded in a JSON string parsed as a single word in HTTP and safely embedded in a JSON string
without further encoding (section 5.1.2 Tracking Status Representation). without further encoding (section 5.5.3 Representation). Since the DNT
Since the DNT header field is intended to be sent on every request, when header field is intended to be sent on every request, when enabled,
enabled, designers of future extensions ought to use as few extension designers of future extensions ought to use as few extension characters as
characters as possible. possible.
ISSUE-111: Different DNT value to signify existence of site-specific
exceptions
Should the user agent send a different DNT value to a first party site if
there exist site-specific exceptions for that first party? (e.g. DNT:2
implies I have Do Not Track enabled but grant permissions to some third
parties while browsing this domain) [OPEN]
4.3 JavaScript API to Detect Preference Note
4.3.1 Interface This document does not have any implied or specified behavior for the
user-agent treatment of cookies when DNT is enabled.
The NavigatorDoNotTrack interface provides a means for the user's tracking 4.3 JavaScript API to Detect Preference
preference to be expressed to web applications running within a page
rendered by the user agent.
[NoInterfaceObject] A doNotTrack attribute on the Navigator interface [NAVIGATOR] (e.g., the
interface NavigatorDoNotTrack { window.navigator object) is hereby defined as the means for expressing the
user's general tracking preference to scripts running within a top-level
page. A user agent MUST provide a doNotTrack attribute on the Navigator
interface for each top-level page.
partial interface Navigator {
readonly attribute DOMString doNotTrack; readonly attribute DOMString doNotTrack;
}; };
4.3.2 Attributes
doNotTrack of type DOMString, readonly doNotTrack of type DOMString, readonly
When a tracking preference is enabled, the doNotTrack attribute When a tracking preference is enabled, the doNotTrack attribute
must have a string value that is the same as the DNT-field-value for each top-level page MUST have the same string value that would
defined in section 4.2 DNT Header Field for HTTP Requests. If a be sent in a DNT-field-value (section 4.2 DNT Header Field for
tracking preference is not enabled, the value is null. HTTP Requests) to an origin server that does not have any
corresponding user-granted exceptions. When a tracking preference
4.3.3 Implements is not enabled, the doNotTrack attribute for each top-level page
MUST have a value of null.
Navigator implements NavigatorDoNotTrack;
Objects implementing the Navigator interface [NAVIGATOR] (e.g., the The doNotTrack attribute only provides the user's general tracking
window.navigator object) must also implement the NavigatorDoNotTrack preference, independent of any user-granted exceptions or out-of-band
interface. An instance of NavigatorDoNotTrack is obtained by using consent. A script wishing to determine the specific tracking preference
binding-specific casting methods on an instance of Navigator. for a given document origin is expected to use the API in section 6.6
Querying a host's exception status.
ISSUE-84: Make DNT status available to JavaScript A user agent MUST provide a doNotTrack attribute value that is consistent
[OPEN] The API above has been deemed inadequate due to origin restrictions with the user's current tracking preference that would be expressed via
on embedded javascript by reference. We are awaiting new text to resolve the DNT header field. However, changes to the user's preference might
this issue. occur between the time when the APIs are checked and an actual request is
made. A server MUST treat the user's most recently received preference as
authoritative.
ISSUE-116: How can we build a JS DOM property which doesn't allow inline Issue 116: How can we build a JS DOM property which doesn't allow inline
JS to receive mixed signals? JS to receive mixed signals?
ISSUE-125: Way to test if a given user agent supports DNT [PENDING REVIEW] Updated text in this section.
4.4 Plug-In APIs 4.4 Plug-In APIs
User agents often include user-installable component parts, commonly known User agents often include user-installable component parts, commonly known
as plug-ins or browser extensions, that are capable of making their own as plug-ins or browser extensions, that are capable of making their own
network requests. From the user's perspective, these components are network requests. From the user's perspective, these components are
considered part of the user agent and thus ought to respect the user's considered part of the user agent and thus ought to respect the user's
configuration of a tracking preference. However, plug-ins do not normally configuration of a tracking preference. However, plug-ins do not normally
have read access to the browser configuration. have read access to the browser configuration.
Note
It is unclear whether we need to standardize the plug-in APIs or if we It is unclear whether we need to standardize the plug-in APIs or if we
should rely on it being defined per user agent based on general advice should rely on it being defined per user agent based on general advice
here. No plug-in APIs have been proposed yet. here. No plug-in APIs have been proposed yet.
4.5 Tracking Preference Expressed in Other Protocols 4.5 Tracking Preference Expressed in Other Protocols
A user's tracking preference is intended to apply in general, regardless A user's tracking preference is intended to apply in general, regardless
of the protocols being used for Internet communication. The protocol of the protocols being used for Internet communication. The protocol
expressed here is specific to HTTP communication; however, the semantics expressed here is specific to HTTP communication; however, the semantics
are not restricted to use in HTTP; the same semantics may be carried by are not restricted to use in HTTP; the same semantics may be carried by
other protocols, either in future revisions of this specification, or in other protocols, either in future revisions of this specification, or in
other specifications. other specifications.
When it is known that the user's preference is for no tracking, compliant When it is known that the user's preference is for no tracking, compliant
services are still required to honor that preference, even if other services are still required to honor that preference, even if other
protocols are used. For example, re-directing to another protocol in order protocols are used. For example, redirecting to another protocol in order
to avoid receipt of the header is not compliant. to avoid receipt of the header is not compliant.
ISSUE-108: Should/could the tracking preference expression be extended to Note
other protocols beyond HTTP?
[PENDING REVIEW] Text in this section; but the last paragraph may be more
appropriate in the compliance document, as it discusses compliance.
5. Communicating a Tracking Status
The next two sections detail two proposals how to communicate tracking
status:
* Well-known URI to allow user agent to retrieve tracking status for a
site
* HTTP Response header to communicate tracking status for a request
This is work in progress. The WG has not yet decided which of these
options (or both) to choose. The WG is currently working on a resolution
but nevertheless appreciates input on this open issue. We are currently
working on a proposal which combines the Tk response header and Tracking
Status Resource. It would make the TSR compulsory and the Tk header
optional. However, it would be required to use the Tk header to notify the
user when something in the TSR has changed in real time.
5.1 Tracking Status Resource
5.1.1 Resource Definition
An origin server must provide a tracking status resource at the well-known
identifier [RFC5785]
/.well-known/dnt
(relative to the URI of that origin server) for obtaining information
about the potential tracking behavior of services provided by that origin
server. A tracking status resource may be used for verification of DNT
support, as described in section 5.1.3 Using the Tracking Status.
A valid retrieval request (e.g., a GET in [HTTP11]) on the well-known URI
must result in either a successful response containing a machine-readable
representation of the site-wide tracking status, as defined below, or a
sequence of redirects that leads to such a representation. A user agent
may consider failure to provide access to such a representation equivalent
to the origin server not implementing this protocol. The representation
might be cached, as described in section 5.1.4 Tracking Status Caching.
If an origin server contains multiple services that are controlled by The last paragraph may be more appropriate in the compliance document, as
distinct parties or that might have differing behavior or policies it discusses compliance.
regarding tracking, then it may also provide a space of well-known
resources for obtaining information about the potential tracking behavior
of each specific service. This parallel tree of resources is called the
tracking status resource space.
The tracking status resource space is defined by the following URI 5. Communicating a Tracking Status
Template [URI-TEMPLATE]:
/.well-known/dnt{+pathinfo} 5.1 Overview
where the value of pathinfo is equal to the path component [RFC3986] of a The primary goals of this protocol-expressing the user's preference and
given reference to that origin server, excluding those references already adhering to that preference-can be accomplished without any response from
within the above resource space. For example, a reference to the server. However, the protocol also seeks to improve the transparency
of tracking behavior by providing a machine-readable means for discovering
claims of compliance and determining the current tracking status.
http://example.com/over/here?q=hello#top Unfortunately, providing a dynamic indication of tracking compliance on
every HTTP response is not feasible, since it would have the effect of
disabling caching for the entire Web. Instead, this protocol defines a
combination of response mechanisms that allow the information to be
communicated without making every response dynamic.
may have a corresponding tracking status resource identified by This section explains how a user agent MAY discover an origin server's
tracking status for a given resource. It defines a REQUIRED site-wide
tracking status resource at a specific well-known location and an OPTIONAL
space of request-specific tracking status resources for sites where the
tracking status might vary based on data within the request. It also
defines a Tk response header field that MAY be sent in any HTTP response,
MUST be sent in responses to requests that modify the tracking status, and
MAY direct the user to a request-specific tracking status resource
applicable to the current request.
http://example.com/.well-known/dnt/over/here 5.2 Tracking Status Value
Resources within the tracking status resource space are represented using A tracking status value is a short notation for communicating how a
the same format as a site-wide tracking status resource. designated resource conforms to the tracking protection protocol, as
defined by this document and [TRACKING-COMPLIANCE]. There is no form of
negative response; i.e., an origin server that does not wish to claim
conformance to this protocol would not supply a tracking status resource
and would not send a Tk header field in responses.
All requests for well-known URIs defined here must not be tracked, For a site-wide tracking status resource, the designated resource to which
irrespective of the presence, value, or absence of a DNT header, cookies, the tracking status applies is any resource on the same origin server. For
or any other information in the request. In addition, all responses to a Tk response header field, the corresponding request target is the
requests on a tracking status resource, including redirected requests, designated resource and remains so for any subsequent request-specific
must not include Set-Cookie or Set-Cookie2 header fields [COOKIES] and tracking status resource referred to by that field.
must not include content that would have the effect of initiating tracking
beyond what is already present for the request. A user agent should ignore
or treat as an error any Set-Cookie or Set-Cookie2 header field received
in such a response.
5.1.2 Tracking Status Representation All of the tracking status mechanisms use a common format for the tracking
status value: a single character from a limited set. The meaning of each
allowed character is defined in the following table.
The representation of a tracking status resource shall be provided in the status meaning
"application/json" format [RFC4627] and must conform to the ABNF in None: The designated resource does not perform tracking of any
section 5.1.5 Tracking Status ABNF. The following is an example tracking N kind, not even for a permitted use, and does not make use of any
status representation that illustrates all of the fields defined by this data collected from tracking.
specification, most of which are optional. First party: The designated resource is designed for use within a
first-party context and conforms to the requirements on a first
1 party. If the designated resource is operated by an outsourced
service provider, the service provider claims that it conforms to
the requirements on a third party acting as a first party.
Third party: The designated resource is designed for use within a
3 third-party context and conforms to the requirements on a third
party.
Dynamic: The designated resource is designed for use in both first
and third-party contexts and dynamically adjusts tracking status
accordingly. If X is present in the site-wide tracking status, more
information MUST be provided via the Tk response header field when
X accessing a designated resource. If X is present in the Tk header
field, more information will be provided in a request-specific
tracking status resource referred to by the status-id. An origin
server MUST NOT send X as the tracking status value in the
representation of a request-specific tracking status resource.
Consent: The designated resource believes it has received prior
consent for tracking this user, user agent, or device, perhaps via
C some mechanism not defined by this specification, and that prior
consent overrides the tracking preference expressed by this
protocol.
Updated: The request resulted in a potential change to the tracking
status applicable to this user, user agent, or device. A user agent
that relies on a cached tracking status SHOULD update the cache
U entry with the current status by making a new request on the
applicable tracking status resource. An origin server MUST NOT send
U as a tracking status value anywhere other than a Tk header field
that is in response to a state-changing request.
{ For the site-wide tracking status and Tk header field, the tracking status
"path": "/", values 1 and 3 indicate how the designated resource is designed to
"tracking": true, conform, not the nature of the request. Hence, if a user agent is making a
"received": "1", request in what appears to be a third-party context and the tracking
"response": "t1", status value indicates that the designated resource is designed only for
"same-site": [ first-party conformance, then either the context has been misunderstood
"example.com", (both are actually the same party) or the resource has been referenced
"example_vids.net", incorrectly. For the request-specific tracking status resource, an
"example_stats.com" indication of first or third party as the status value describes how the
], resource conformed to that specific request, and thus indicates both the
"partners": [ nature of the request (as viewed by the origin server) and the applicable
"api.example-third-party.com" set of requirements to which the origin server claims to conform.
],
"policy": "/tracking.html",
"edit": "http://example-third-party.com/your/data",
"options": "http://example-third-party.com/your/consent"
}
A tracking status representation consists of a single status-object The tracking status value is case sensitive, as defined formally by the
containing members that describe the tracking status applicable to this following ABNF.
user agent's request.
If the status-object has an optional path member, then this object tracking-v = "1" ; "1" - first-party
describes the tracking status for the entire space of resources that share / "3" ; "3" - third-party
the same path prefix as the value of path. The user agent must interpret / %x43 ; "C" - consent
the path value relative to the originally referenced resource, not the / %x4E ; "N" - none
resource where it obtained the tracking status representation. / %x55 ; "U" - updated
/ %x58 ; "X" - dynamic
For the site-wide tracking status resource, the presence of a path member Issue 137: Does hybrid tracking status need to distinguish between first
with a value of "/" indicates that this status-object applies for the party (1) and outsourcing service provider acting as a first party (s)
entire origin server of the originally referenced resource. If the
originally referenced resource's path component does not share the same
prefix as the value of path, or if the path member is absent, then the
tracking status for the referenced resource may be obtained via a request
on the corresponding tracking status resource space.
A status-object must have a member named tracking with a boolean value. A [PENDING REVIEW] No, in practice there may be dozens of service providers
value of false indicates that the corresponding resources do not perform on any given request. If the designated resource is operated by a service
tracking as it is defined by [TRACKING-COMPLIANCE]. A value of true provider acting as a first party, then the responsible first party is
indicates that the corresponding resource performs tracking and claims to identified by the policy link or the owner of the origin server domain.
conform to all tracking compliance requirements applicable to this site. This satisfies the use case of distinguishing between a service provider
acting for some other site and the same service provider acting on one of
its own sites.
For example, the following demonstrates a minimal tracking status 5.3 Tracking Status Qualifier Values
representation that is applicable to any resource that does not perform
tracking.
{"tracking": false} When present, the tracking status qualifier member's value consists of a
string of characters indicating what permitted uses for tracking are being
used. Multiple qualifiers can be provided.
The following status-object would indicate that the entire site does not Issue 136: Resolve dependencies of the TPE on the compliance specification
perform tracking.
{"path": "/", "tracking": false} The list of qualifiers is intended to match one to one to the permitted
uses identified by [TRACKING-COMPLIANCE], using references to the
definitions there. The list will then be updated accordingly.
If tracking is true, the status-object must include two additional qualifier meaning
members, named received and response, and may include other members as Audit: Tracking is limited to that necessary for an external
described below. a audit of the service context and the data collected is minimized
accordingly.
c Ad frequency capping: Tracking is limited to frequency capping
and the data collected is minimized accordingly.
Fraud prevention: Tracking is limited to that necessary for
f preventing or investigating fraudulent behavior and security
violations; the data collected is minimized accordingly.
Local constraints: Tracking is limited to what is required by
l local law, rule, or regulation and the data collected is
minimized accordingly.
r Referrals: Tracking is limited to collecting referral
information and the data collected is minimized accordingly.
The received member must have either a string value equal to the Qualifiers that indicate limitations on tracking correspond to the
DNT-field-value received in that request or the value null if no specific permitted uses in [TRACKING-COMPLIANCE]. An origin server
DNT-field-value was received. Any invalid characters received in the indicating one or more of those permitted uses also indicates that it
DNT-field-value must be elided from the string value to ensure that conforms to the requirements associated with those permitted uses.
invalid data is not injected into the JSON result. Multiple limitation qualifiers mean that multiple permitted uses of
tracking might be present and that each such use conforms to the
associated requirements. All limitation qualifiers imply some form of
tracking might be used and thus MUST NOT be provided with a tracking
status value of N (not tracking).
The response member must have a string value that indicates the status of Future extensions to this protocol might define additional characters as
tracking applicable specifically to this user in light of the received qualifiers from the ext-qualifier set (consisting of the remaining unused
DNT-field-value. The string value begins with "t" (tracking) or "n" (not lowercase letters, dot, dash, and underscore). Recipients SHOULD ignore
tracking) and may be followed by alphanumeric characters that indicate extension qualifiers that they do not understand.
reasons for that status, as described in the following table.
reasons meaning The tracking qualifier value is case sensitive, as defined formally by the
1 Designed for use as a first-party only following ABNF.
3 Designed for use as a third-party
a Limited to advertising audits
c Prior consent received from this user agent
f Limited to fraud prevention
g For compliance with regional/geographic
constraints
q Limited to advertising frequency capping
r Limited to referral information
An optional member named same-site may be provided with an array value tracking-q = tracking-q-v*
containing a list of domain names that the origin server claims are the tracking-q-v = %x61 ; "a" - audit
same site, to the extent they are referenced on this site, since all data / %x63 ; "c" - capping
collected via those references share the same data controller. / %x66 ; "f" - fraud
/ %x6C ; "l" - local
/ %x72 ; "r" - referral
An optional member named partners may be provided with an array value 5.4 Tk Header Field for HTTP Responses
containing a list of domain names for third-party services that might
track the user as a result of using this site and which do not have the
same data controller as this site.
An optional member named policy may be provided with a string value 5.4.1 Definition
containing a URI-reference to a human-readable document that describes the
tracking policy for this site. The content of such a policy document is
beyond the scope of this protocol and only supplemental to what is
described by this machine-readable tracking status representation.
An optional member named edit may be provided with a string value The Tk response header field is hereby defined as an OPTIONAL means for
containing a URI-reference to a resource intended to allow a tracked user indicating the tracking status that applied to the corresponding request
agent to review or delete data collected by this site, if any such data and as a REQUIRED means for indicating that a state-changing request has
remains associated with this user agent. The design of such a resource and resulted in an interactive change to the tracking status.
the extent to which it can provide access to that data is beyond the scope
of this protocol.
An optional member named options may be provided with a string value Tk-field-name = "Tk" ; case-insensitive
containing a URI-reference to a resource intended to allow a user agent to Tk-field-value = tracking-v [tracking-q] [ ";" status-id ]
opt-in, opt-out, or otherwise modify their consent status regarding data
collection by this site. The design of such a resource and how it might
implement an out-of-band consent mechanism is beyond the scope of this
protocol.
Additional extension members may be provided in the status-object to The Tk field-value begins with a tracking status value (section 5.2
support future enhancements to this protocol. A user agent should ignore Tracking Status Value), optionally followed by one or more tracking
extension members that it does not recognize. qualifiers (section 5.3 Tracking Status Qualifier Values), and then
optionally a semicolon and a status-id that refers to a request-specific
tracking status resource (section 5.4.2 Referring to a Request-specific
Tracking Status Resource).
Note that the tracking status resource space applies equally to both For example, a Tk header field for a resource that claims not to be
first-party and third-party services. An example of a third-party tracking tracking would look like:
status is
{ Example 2
"tracking": true,
"received": "1",
"response": "n",
"policy": "/privacy.html",
"edit": "/your/data",
"options": "/your/consent"
}
ISSUE-47: Should the response from the server indicate a policy that Tk: N
describes the DNT practices of the server?
[PENDING REVIEW] The tracking status resource is a machine-readable policy
and provides a mechanism for supplying a link to a human-readable policy.
ISSUE-61: A site could publish a list of the other domains that are whereas a Tk header field for a resource that might perform tracking
associated with them (though not necessarily for every request) and conforms to the third-party
[PENDING REVIEW] The same-site and partners members provide a means to requirements of [TRACKING-COMPLIANCE], while claiming the audit exception,
list first-party and third-party domains, respectively. would look like:
ISSUE-124: Alternative DNT implementations that replace HTTP headers with Example 3
something else
[PENDING REVIEW] The tracking status resource minimizes bandwidth usage
because only a small proportion of user agents are expected to perform
active verification, status would only be requested once per site per day,
and the response can be extensively cached.
5.1.3 Using the Tracking Status Tk: 3a
A key advantage of providing the tracking status at a resource separate 5.4.2 Referring to a Request-specific Tracking Status Resource
from the site's normal services is that the status can be accessed and
reviewed prior to making use of those services and prior to making
requests on third-party resources referenced by those services. In
addition, the presence (or absence) of a site-wide tracking status
representation is a means for testing deployment of this standard and
verifying that a site's claims regarding tracking are consistent with the
site's observed behavior over time.
A user agent may check the tracking status for a given resource URI by If an origin server has multiple, request-specific tracking policies, such
making a retrieval request for the well-known address /.well-known/dnt that the tracking status might differ depending on some aspect of the
relative to that URI. request (e.g., method, target URI, header fields, data, etc.), the origin
server MAY provide an additional subtree of well-known resources
corresponding to each of those distinct tracking statuses. The OPTIONAL
status-id portion of the Tk field-value indicates which specific tracking
status resource applies to the current request.
If the response is an error, then the service does not implement this status-id = 1*id-char ; case-sensitive
standard. If the response is a redirect, then follow the redirect to id-char = ALPHA / DIGIT / "_" / "-" / "+" / "=" / "/"
obtain the tracking status (up to some reasonable maximum of redirects to
avoid misconfigured infinite request loops). If the response is
successful, obtain the tracking status representation from the message
payload, if possible, or consider it an error.
Once the tracking status representation is obtained, parse the For example, a response containing
representation as JSON to extract the Javascript status-object. If parsing
results in a syntax error, the user agent should consider the site to be
non-conformant with this protocol.
If the status-object does not have a member named path or if the value of Example 4
path is not "/" and not a prefix of the path component for the URI being
checked, then find the service-specific tracking status resource by taking
the template /.well-known/dnt{+pathinfo} and replacing {+pathinfo} with
the path component of the URI being checked. Perform a retrieval request
on the service-specific tracking status resource and process the result as
described above to obtain the specific tracking status.
The status-object is supposed to have a member named tracking with a Tk: 1;fRx42
boolean value. If the value is false, then no tracking is performed for
the URI being checked. If the value is true, then examine the member named
received to verify that the DNT header field sent by the user agent has
been correctly received by the server. If the received value is incorrect,
there may be an intermediary interfering with transmission of the DNT
request header field.
If the received value is correct, then examine the member named response indicates that the target resource claims to conform to the first-party
to see what the origin server has claimed regarding the tracking status requirements of [TRACKING-COMPLIANCE] and that an applicable tracking
for this user agent in light of the received DNT-field-value. status representation can be obtained by performing a retrieval request on
If the first character of the response value is "n", then the origin /.well-known/dnt/fRx42
server claims that it will not track the user agent for requests on the
URI being checked, and for any URIs with a path prefix matching the path
member's value, for at least the next 24 hours or until the Cache-Control
information indicates that this response expires, as described below.
If the first character of the response value is "t", then the origin If a Tk field-value has a tracking status value of X (dynamic), then a
server claims that it might track the user agent for requests on the URI status-id MUST be included in the field-value.
being checked, and for any URIs with a path prefix matching the path
member's value, for at least the next 24 hours or until the Cache-Control
information indicates that this response expires.
The remaining characters of the response value might indicate reasons for 5.4.3 Indicating an Interactive Status Change
the above choices or limitations that the origin server will place on its
tracking.
The others members of the status-object may be used to help the user agent We anticipate that interactive mechanisms might be used, beyond the scope
differentiate between a site's first-party and third-party services, to of this specification, that have the effect of asking for and obtaining
provide links to additional human-readable information related to the prior consent for tracking, or for modifying prior indications of consent.
tracking policy, and to provide links for control over past data collected For example, the tracking status resource's status-object defines a
or over some consent mechanism outside the scope of this protocol. control member that can refer to such a mechanism. Although such
out-of-band mechanisms are not defined by this specification, their
presence might influence the tracking status object's response value.
5.1.4 Tracking Status Caching When an origin server provides a mechanism via HTTP for establishing or
modifying out-of-band tracking preferences, the origin server MUST
indicate within the mechanism's response when a state-changing request has
resulted in a change to the tracking status for that server. This
indication of an interactive status change is accomplished by sending a Tk
header field in the response with a tracking status value of U (updated).
If the tracking status is applicable to all users, regardless of the Example 5
received DNT-field-value or other data received via the request, then the
response should be marked as cacheable and assigned a time-to-live
(expiration or max-use) that is sufficient to enable shared caching but
not greater than the earliest point at which the service's tracking
behavior might increase. For example, if the tracking status response is
set to expire in seven days, then the earliest point in time that the
service's tracking behavior can be increased is seven days after the
policy has been updated to reflect the new behavior, since old copies
might persist in caches until the expiration is triggered. A service's
tracking behavior can be reduced at any time, with or without a
corresponding change to the tracking status resource.
If the tracking status is only applicable to all users that have the same Tk: U
DNT-field-value, then either the response must include a Cache-Control
header field with one of the directives "no-cache", "no-store",
"must-revalidate", or "max-age=0", or the response must include a Vary
header field that includes "DNT" in its field-value.
If the tracking status is only applicable to the specific user that 5.5 Tracking Status Resource
requested it, then the response must include a Cache-Control header field
with one of the directives "no-cache", "no-store", "must-revalidate", or
"max-age=0".
Regardless of the cache-control settings, it is expected that user agents 5.5.1 Site-wide Tracking Status
will check the tracking status of a service only once per session (at
most). A public Internet site that intends to change its tracking status
to increase tracking behavior must update the tracking status resource in
accordance with that planned behavior at least twenty-four hours prior to
activating that new behavior on the service.
5.1.5 Tracking Status ABNF An origin server MUST provide a site-wide tracking status resource at the
well-known identifier [RFC5785]
The representation of a site's machine-readable tracking status must /.well-known/dnt
conform to the following ABNF for status-object, except that the members
within each member-list may be provided in any order.
status-object = begin-object member-list end-object (relative to the URI of that origin server) for obtaining information
member-list = [ path ns path-v vs ] about the potential tracking behavior of resources provided by that origin
tracking ns tracking-v server. A tracking status resource MAY be used for verification of DNT
[ vs received ns received-v ] support, as described in section 5.7 Using the Tracking Status.
[ vs response ns response-v ]
[ vs same-site ns same-site-v ]
[ vs partners ns partners-v ]
[ vs policy ns policy-v ]
[ vs edit ns edit-v ]
[ vs options ns options-v ]
*( vs extension )
path = %x22 "path" %x22 A valid retrieval request (e.g., a GET in HTTP) on the well-known URI MUST
path-v = string ; URI absolute-path result in either a successful response containing a machine-readable
representation of the site-wide tracking status, as defined below, or a
sequence of redirects that leads to such a representation. A user agent
MAY consider failure to provide access to such a representation equivalent
to the origin server not implementing this protocol. The representation
MAY be cached, as described in section 5.5.5 Caching.
tracking = %x22 "tracking" %x22 5.5.2 Request-specific Tracking Status
tracking-v = true / false
If an origin server has multiple, request-specific tracking policies, such
that the tracking status might differ depending on some aspect of the
request (e.g., method, target URI, header fields, data, etc.), the origin
server MAY provide an additional subtree of well-known resources
corresponding to each of those distinct tracking statuses. The Tk response
header field (section 5.4 Tk Header Field for HTTP Responses) can include
a status-id to indicate which specific tracking status resource applies to
the current request.
received = %x22 "received" %x22 The tracking status resource space is defined by the following URI
received-v = null / string Template [URI-TEMPLATE]:
response = %x22 "response" %x22 /.well-known/dnt{/status-id}
response-v = %x22 r-codes %x22
r-codes = ("t" / "n") *reasons where the value of status-id is a string of URI-safe characters provided
by a Tk field-value in response to a prior request. For example, a prior
response containing
Example 6
reasons = "1" ; first-party Tk: 1;ahoy
/ "3" ; third-party
/ "a" ; advertising audits
/ "c" ; prior consent
/ "f" ; fraud prevention
/ "g" ; geographic/regional compliance
/ "q" ; frequency capping
/ "r" ; referrals
/ ALPHA / DIGIT ; TBD
same-site = %x22 "same-site" %x22 refers to the specific tracking status resource
same-site-v = array-of-strings
partners = %x22 "partners" %x22 /.well-known/dnt/ahoy
partners-v = array-of-strings
policy = %x22 "policy" %x22 Resources within the request-specific tracking status resource space are
represented using the same format as a site-wide tracking status resource.
policy-v = string ; URI-reference 5.5.3 Representation
edit = %x22 "edit" %x22 The representation of a tracking status resource shall be provided in the
edit-v = string ; URI-reference "application/json" format [RFC4627] and MUST conform to the ABNF for
status-object (except that the members within each member-list MAY be
provided in any order).
options = %x22 "options" %x22 The following example tracking status representation illustrates all of
options-v = string ; URI-reference the fields defined by this specification, most of which are optional.
extension = object Example 7
{
"tracking": "1",
"same-party": [
"example.com",
"example_vids.net",
"example_stats.com"
],
"third-party": [
"api.example.net"
],
"audit": [
"http://auditor.example.org/727073"
],
"policy": "/tracking.html",
"control": "http://example.com/your/data"
}
array-of-strings = begin-array A tracking status representation consists of a single status-object
[ string *( vs string ) ] containing members that describe the tracking status applicable to the
end-array designated resource.
ns = <name-separator (:), as defined in [RFC4627]> status-object = begin-object member-list end-object
vs = <value-separator (,), as defined in [RFC4627]>
begin-array = <begin-array ([), as defined in [RFC4627]> member-list = tracking ns tracking-v [tracking-q]
end-array = <end-array (]), as defined in [RFC4627]> [ vs same-party ns same-party-v ]
begin-object = <begin-object ({), as defined in [RFC4627]> [ vs third-party ns third-party-v ]
[ vs audit ns audit-v ]
[ vs policy ns policy-v ]
[ vs control ns control-v ]
*( vs extension )
end-object = <end-object (}), as defined in [RFC4627]> A status-object MUST have a member named tracking that contains a single
object = <object, as defined in [RFC4627]> character tracking status value (section 5.2 Tracking Status Value),
string = <string, as defined in [RFC4627]> optionally followed by one or more tracking qualifiers (section 5.3
Tracking Status Qualifier Values) .
true = <true, as defined in [RFC4627]> tracking = %x22 "tracking" %x22
false = <false, as defined in [RFC4627]>
null = <null, as defined in [RFC4627]>
For example, the following demonstrates a minimal tracking status
representation that is applicable to any resource that does not perform
tracking.
5.2 Tk Header Field for HTTP Responses Example 8
5.2.1 Motivation {"tracking": "N"}
This specification defines an HTTP response header, in order to meet the An OPTIONAL member named same-party MAY be provided with an array value
following needs: containing a list of domain names that the origin server claims are the
same party, to the extent they are referenced by the designated resource,
since all data collected via those references share the same data
controller.
* User-agents can confirm that the server with which they are same-party = %x22 "same-party" %x22
communicating has received their DNT request. same-party-v = array-of-strings
* User-agents can determine which class of practices the server intends
to follow when processing this particular request.
* User-agents can determine if a server believes that the user has
out-of-band consented to let them do additional tracking, and may be
able to review or modify that consent.
* Servers make a clear promise about how they will process data gathered
from this particular request.
* Servers have a well-known place to point to more information about
their tracking/privacy practice.
* Servers can provide customized information to clients if desired.
An origin server may indicate the tracking status for a particular request An OPTIONAL member named third-party MAY be provided with an array value
by including a Tk header field in the corresponding response. If a request containing a list of domain names for third-party services that might be
contains a DNT-field-value starting with "1", an origin server should send invoked while using the designated resource but do not share the same data
a Tk header field in the corresponding response. controller as the designated resource.
If an origin server chooses not to send a Tk header field, then the user third-party = %x22 "third-party" %x22
agent will not know if the tracking preference has been received or if it third-party-v = array-of-strings
will be honored. This may have negative consequences for the site, such as
triggering preventive measures on the user agent or being flagged as
non-compliant by tools that look for response header fields.
ISSUE-107: Exact format of the response header? An OPTIONAL member named audit MAY be provided with an array value
[PENDING REVIEW] See the proposal in this section. containing a list of URI references to external audits of the designated
resource's tracking policy and tracking behavior in compliance with this
protocol. Preferably, the audit references are to resources that describe
the auditor and the results of that audit; however, if such a resource is
not available, a reference to the auditor is sufficient.
ISSUE-120: Should the response header be mandatory (must) or recommended audit = %x22 "audit" %x22
(should) audit-v = array-of-strings
[PENDING REVIEW] Text in above paragraphs.
5.2.2 Tk ABNF An OPTIONAL member named policy MAY be provided with a string value
containing a URI-reference to a human-readable document that describes the
tracking policy for the designated resource. The content of such a policy
document is beyond the scope of this protocol and only supplemental to
what is described by this machine-readable tracking status representation.
The Tk header field is defined as follows: policy = %x22 "policy" %x22
policy-v = string ; URI-reference
Tk-Response = "Tk:" [CFWS] Tk-Status [CFWS] [ opt-in-flag ] [C If the tracking status value is 1 and the designated resource is being
FWS] [ reason-code ] operated by an outsourced service provider on behalf of a first party, the
Tk-Status = no-dnt origin server MUST identify the responsible first party via the domain of
/ not-tracking the policy URI, if present, or by the domain owner of the origin server.
/ first-party If no policy URI is provided and the origin server domain is owned by the
/ service-provider service provider, then the service provider is the first party.
no-dnt = "0"
not-tracking = "1"
first-party = %x66 ; lowercase f
service-provider = %x73 ; lowercase s
opt-in-flag = "1"
reason-code = ALPHA
5.2.3 Tk Semantics An OPTIONAL member named control MAY be provided with a string value
containing a URI-reference to a resource for giving the user control over
personal data collected by the designated resource (and possibly other
resources); a control member SHOULD be provided if the tracking status
value indicates prior consent (C). Such a control resource might include
the ability to review past data collected, delete some or all of the data,
provide additional data (if desired), or opt-in, opt-out, or otherwise
modify an out-of-band consent status regarding data collection. The design
of such a resource, the extent to which it can provide access to that
data, and how one might implement an out-of-band consent mechanism is
beyond the scope of this protocol.
Tk: 0 (no-dnt) indicates that this party does not comply with control = %x22 "control" %x22
[TRACKING-COMPLIANCE]. control-v = string ; URI-reference
Tk: 1 (not-tracking) indicates that: Additional extension members MAY be provided in the status-object to
support future enhancements to this protocol. A user agent SHOULD ignore
extension members that it does not recognize.
* this party complies with [TRACKING-COMPLIANCE], and extension = object
* this party will process this request according to the specification
for 3rd parties in [TRACKING-COMPLIANCE].
Tk: f (first-party) indicates that: array-of-strings = begin-array
[ string *( vs string ) ]
end-array
* this party complies with [TRACKING-COMPLIANCE], ns = <name-separator (:), as defined in [[!RFC4627]]>
* this resource is intended to be served as a first party, and vs = <value-separator (,), as defined in [[!RFC4627]]>
* this party will process this request according to the specifications
for 1st parties in [TRACKING-COMPLIANCE].
Tk: s (service-provider) indicates that: begin-array = <begin-array ([), as defined in [[!RFC4627]]>
end-array = <end-array (]), as defined in [[!RFC4627]]>
begin-object = <begin-object ({), as defined in [[!RFC4627]]>
end-object = <end-object (}), as defined in [[!RFC4627]]>
object = <object, as defined in [[!RFC4627]]>
string = <string, as defined in [[!RFC4627]]>
true = <true, as defined in [[!RFC4627]]>
false = <false, as defined in [[!RFC4627]]>
null = <null, as defined in [[!RFC4627]]>
* this party complies with [TRACKING-COMPLIANCE], Note that the tracking status resource space applies equally to both
* this resource is intended to be used in the context of third party first-party and third-party services. An example of a third-party tracking
acting as an outsourced service provider for a first party, and status is
* this party will process this request according to the exemption for a
third party acting as an outsourced service provider for a first
party, as described in [TRACKING-COMPLIANCE].
The opt-in-flag indicates that the server believes that the user has Example 9
affirmatively consented to allow this party additional permission to track
them. Unless the opt-in-flag is included, the server asserts that will act
in responding to this request as if the user has not affirmatively
consented to allow this party additional permission to track them.
The reason-code can be used when requesting more information (see below). {
"tracking": "3",
"policy": "/privacy.html",
"control": "/your/data",
}
5.2.4 More Information 5.5.4 Status Checks are Not Tracked
If a reason code is specified in the response, the well-known resource When sending a request for the tracking status, a user agent SHOULD
defined here must exist; if an opt-in-flag is included, the wel--known include any cookie data [COOKIES] (set prior to the request) that would be
resource defined here should exist; otherwise it may exist. sent in a normal request to that origin server, since that data might be
needed by the server to determine the current tracking status. For
example, the cookie data might indicate a prior out-of-band decision by
the user to opt-out or consent to tracking by that origin server.
The user can understand and manage their opt-in by visiting the well-known All requests on the tracking status resource space, including the
URI site-wide tracking status resource, MUST NOT be tracked, irrespective of
the presence, value, or absence of a DNT header field, cookies, or any
other information in the request. In addition, all responses to those
requests, including the responses to redirected tracking status requests,
MUST NOT have Set-Cookie or Set-Cookie2 header fields and MUST NOT have
content that initiates tracking beyond what was already present in the
request. A user agent SHOULD ignore, or treat as an error, any Set-Cookie
or Set-Cookie2 header field received in such a response.
/.well-known/dnt?status={Tk-status}&opt-in={opt-in-flag}&r={reason-code} 5.5.5 Caching
relative to the request-target. If the tracking status is applicable to all users, regardless of the
received DNT-field-value or other data received via the request, then the
response SHOULD be marked as cacheable and assigned a time-to-live
(expiration or max-use) that is sufficient to enable shared caching but
not greater than the earliest point at which the service's tracking
behavior might increase. For example, if the tracking status response is
set to expire in seven days, then the earliest point in time that the
service's tracking behavior can be increased is seven days after the
policy has been updated to reflect the new behavior, since old copies
might persist in caches until the expiration is triggered. A service's
tracking behavior can be reduced at any time, with or without a
corresponding change to the tracking status resource.
The information at this URI provides additional information about this If the tracking status is only applicable to all users that have the same
party's privacy practices and practices, particularly concerning the DNT-field-value, then the response MUST either be marked with a Vary
opt-in-flag. header field that includes "DNT" in its field-value or marked as not
reusable by a shared cache without revalidation with a Cache-Control
header field containing one of the following directives: "private",
"no-cache", "no-store", or "max-age=0".
The above well-known URI has not yet been reconciled with the similar but If the tracking status is only applicable to the specific user that
distinct definition for the tracking status resource. We anticipate that requested it, then the response MUST include a Cache-Control header field
one or the other will be adopted, or the two proposals will be merged. containing one of the following directives: "private", "no-cache", or
"no-store".
5.2.5 Implementation and Usage Considerations Regardless of the cache-control settings, it is expected that user agents
will check the tracking status of a service only once per session (at
most). A public Internet site that intends to change its tracking status
to increase tracking behavior MUST update the tracking status resource in
accordance with that planned behavior at least twenty-four hours prior to
activating that new behavior on the service.
Implementers should use caution when allowing caching of resources on A user agent that adjusts behavior based on active verification of
which an opt-in flag is included. If caching is not carefully managed, tracking status, relying on cached tracking status responses to do so,
there is a risk of sending a response intended for opted-in users to users SHOULD check responses to its state-changing requests (e.g., POST, PUT,
who haven't opted in. DELETE, etc.) for a Tk header field with the U tracking status value, as
described in section 5.4.3 Indicating an Interactive Status Change.
Implementers should carefully choose the cache properties of the items at 5.6 Status Code for Tracking Required
the well-known URI. The content at these locations must be correct for the
entire cache duration, otherwise users who load stale cached copies of
these resources may be misled.
Any party can use the not-tracking response: this response just indicates If an origin server receives a request with DNT:1, does not have
a behavior. If a first party complies with the third-party definition, out-of-band consent for tracking this user, and wishes to deny access to
they are free to send this response. However, the first-party and service the requested resource until the user provides some form of user-granted
provider responses indicate both a behavior and an intention about that exception or consent for tracking, then the origin server SHOULD send an
party's status. It would be deceptive to send the first-party header on a HTTP error response with a status code of 409 (Conflict) and a message
resource which is only ever embedded as a third party. body that describes why the request has been refused and how one might
supply the required consent or exception to avoid this conflict [HTTP11].
The no-dnt response should not be used on requests which are processed in The 409 response SHOULD include a user authentication mechanism in the
accordance with [TRACKING-COMPLIANCE]. An entity which implements DNT header fields and/or message body if user login is one of the ways through
should not use this response. which access is granted.
When embedding content from other sites, consider how that site expects 5.7 Using the Tracking Status
their content to be used. If you embed/link to an object on another site,
it's possible that the resource will send a first-party response even
though it is now in a third-party context because the designer of that
site never intended that object to be embedded. If a resource always sends
a third-party response, there is no risk of this inconsistent response.
Only the first-party outsourcer of service-provider objects should ever
embed them.
5.2.6 Examples Note
Tk: 1 This section is for collecting use cases that describe questions a user
agent might have about tracking status and how the protocol can be used to
answer such questions. More cases are needed.
The site is a third or first party, in compliance with the definitions of 5.7.1 Discovering Deployment
a 3rd party that is not tracking.
Tk: 1 1 agreed The presence of a site-wide tracking status representation is a claim that
the service conforms to this protocol for a given user agent. Hence,
deployment of this protocol for a given service can be discovered by
making a retrieval request on the site-wide tracking resource
/.well-known/dnt relative to the service URI.
The site is a third party, that believes it has an explicit opt-in from If the response is an error, then the service does not implement this
the user; more information can be found at: standard. If the response is a redirect, then follow the redirect to
obtain the tracking status (up to some reasonable maximum of redirects to
avoid misconfigured infinite request loops). If the response is
successful, obtain the tracking status representation from the message
payload, if possible, or consider it an error.
/.well-known/dnt?status=1&opt-in=1&r=agreed 5.7.2 Preflight Checks
5.3 Status Code for Tracking Required A key advantage of providing the tracking status at a resource separate
from the site's normal services is that the status can be accessed and
reviewed prior to making use of those services and prior to making
requests on third-party resources referenced by those services.
An HTTP error response status code might be useful for indicating that the A user agent MAY check the tracking status for a designated resource by
site refuses service unless the user either logs into a subscription first making a retrieval request for the site-wide tracking status
account or agrees to an exception to DNT for this site and its contracted representation, as described above, and then parsing the representation as
third-party sites. JSON to extract the Javascript status-object. If retrieval is unsuccessful
or parsing results in a syntax error, the user agent SHOULD consider the
site to be non-conformant with this protocol.
6. Site-specific Exceptions The status-object is supposed to have a member named tracking containing
the tracking status value. The meaning of each tracking status value is
defined in section 5.2 Tracking Status Value.
ISSUE-118: Should requesting a user-agent-managed site-specific exception If the tracking status value is N, then the origin server claims that no
be asynchronous? tracking is performed for the designated resource for at least the next 24
[PENDING REVIEW] As proposed below. hours or until the Cache-Control information indicates that this response
expires.
ISSUE-115: Should sites be able to manage site-specific tracking If the tracking status value is not N, then the origin server claims that
exceptions outside of the user-agent-managed system? it might track the user agent for requests on the URI being checked for at
least the next 24 hours or until the Cache-Control information indicates
that this response expires.
ISSUE-111: Different DNT values to signify existence of site-specific 6. User-Granted Exceptions
exception
6.1 Overview 6.1 Overview
This section is non-normative. This section is non-normative.
Exceptions to Do Not Track, including site-specific exceptions, are User-granted exceptions to Do Not Track, including site-specific
managed by the user agent. A resource should rely on the DNT header it exceptions, are managed by the user agent. A resource should rely on the
receives to determine the user's preference for tracking with respect to DNT header it receives to determine the user's preference for tracking
that particular request. An API is provided so that sites may request and with respect to that particular request. An API is provided so that sites
check the status of exceptions for tracking. may request and check the status of exceptions for tracking.
We anticipate that many user-agents might provide a prompt to users when We anticipate that many user-agents might provide a prompt to users when
this API is used, or to store exceptions. Questions of user interface this API is used, or to store exceptions. Questions of user interface
specifics - for granting, configuring, storing, syncing and revoking specifics - for granting, configuring, storing, syncing and revoking
exceptions - are explicitly left open to implementers. exceptions - are explicitly left open to implementers.
6.2 Motivating principles and use cases Issue 144: What constraints on user agents should be imposed for
user/granted exceptions
[OPEN] but mostly addressed in the proposal here.
6.2 Motivating Principles and Use Cases
This section is non-normative. This section is non-normative.
The following principles guide the design of the user-agent-managed The following principles guide the design of user-agent-managed
site-specific exceptions proposal. exceptions.
* Content providers may wish to prompt visitors to their properties to * Content providers may wish to prompt visitors to their properties to
"opt back in" to tracking for behavioral advertising or similar opt back in to tracking for behavioral advertising or similar purposes
purposes when they arrive with the Do Not Track setting enabled. when they arrive with the Do Not Track setting enabled.
* Privacy-conscious users may wish to view or edit all the site-specific * Privacy-conscious users may wish to view or edit all the exceptions
exceptions they've granted in a single, consistent user interface, they've granted in a single, consistent user interface, rather than
rather than managing preferences in a different way on every content managing preferences in a different way on every content provider or
provider or tracker's privacy page. tracker's privacy page.
* Granting an exception in one context (while browsing a news site) * Granting an exception in one context (while browsing a news site)
should not apply that exception to other contexts (browsing a medical should not apply that exception to other contexts (browsing a medical
site) that may not be expected. site) that may not be expected.
* Tracking providers should not ever have to second-guess a user's * Tracking providers should not ever have to second-guess a user's
expressed Do Not Track preference. expressed Do Not Track preference.
* The solution should not require cross-domain communication between a * The solution should not require cross-domain communication between a
first party publisher and its third party trackers. first-party publisher and its third parties.
When asking for a site-specific exception, the top-level domain making the
request may be making some implicit or explicit claims as to the actions
and behavior of its third parties; for this reason, it might want to
establish exceptions for only those for which it is sure that those claims
are true. (Consider a site that has some trusted advertisers and analytics
providers, and some mashed-up content from less-trusted sites). For this
reason, there is support both for explicitly named sites, as well as
support for granting an exception to all third-parties on a given site
(site-wide exception, using the conceptual wild-card "*").
There are some cases in which a user may desire a site to be allowed to
track them on any top-level domain. An API is provided so that the site
and the user may establish such a web-wide exception.
6.3 Exception model 6.3 Exception model
6.3.1 Site pairs 6.3.1 Introduction
This section describes the effect of the APIs in terms of a logical
processing model; this model describes the behavior, but should not be
read as mandating any specific implementation.
This API considers exceptions which are double-keyed to two domains: the This API considers exceptions which are double-keyed to two domains: the
site, and the tracker. A user might - for instance - want AnalytiCo to site, and the target. A user might - for instance - want AnalytiCo to be
track them on Example News, but not on Example Medical. To simplify allowed to track them on Example News, but not on Example Medical. To
language used in this API specification, we define two terms: simplify language used in this API specification, we define three terms:
* This site is the domain name of the top-level document origin of this * Top-Level Domain (TLD) is the domain name of the top-level document
DOM: essentially the fully qualified domain name in the address bar. origin of this DOM: essentially the fully qualified domain name in the
* A tracker is a domain name which is not operated by the same party address bar.
which operates this site, and which may be an origin for embedded * A target site is a domain name which is the target of an HTTP request,
resources on this site. and which may be an origin for embedded resources on the indicated
top-level domain.
* The document origin of a script is the domain of origin of the
document that caused that script to be loaded (not necessarily the
same as the origin of the script itself).
For instance, if the document at For instance, if the document at
http://web.exnews.com/news/story/2098373.html references the resources http://web.exnews.com/news/story/2098373.html references the resources
http://exnews.analytico.net/1x1.gif and http://exnews.analytico.net/1x1.gif and
http://widgets.exsocial.org/good-job-button.js, this site is http://widgets.exsocial.org/good-job-button.js, the top-level domain is
web.exnews.com; exnews.analytico.net and widgets.exsocial.org are both web.exnews.com; exnews.analytico.net and widgets.exsocial.org are both
trackers. targets.
ISSUE-112: How are sub-domains handled for site-specific exceptions? Issue 112: How are sub-domains handled for site-specific exceptions?
Should a request for a tracking exception apply to all subdomains of the
first party making the request? Or should a first party explicitly list [PENDING REVIEW] Should a request for a tracking exception apply to all
the subdomains that it's asking for? Similarly, should third party subdomains of the first party making the request? Or should a first party
subdomains be allowed (e.g. *.tracker.com)? explicitly list the subdomains that it's asking for? Similarly, should
third-party subdomains be allowed (e.g. *.tracker.com)?
Proposal: Exceptions are requested for fully-qualified domain names. Proposal: Exceptions are requested for fully-qualified domain names.
The domains that enter into the behavior of the APIs include:
* As described above, the document origin active at the time of the
call, and;
* Domain names passed to the API.
Domains that enter into the decision over what DNT header to be sent in a
given HTTP request include:
* The top-level domain of the current context;
* The target of the HTTP request.
Note
Note that these strict, machine-discoverable, concepts may not match the
definitions of first and third party; in particular, sites themselves need
to determine (and signal) when they get 'promoted' to first party by
virtue of user interaction; the UA will not change the DNT header it sends
them.
The calls cause the following steps to occur:
* First, the UA somehow confirms with the user that they agree to the
grant of exception, if not already granted;
* If they agree, then the UA adds to its local database one or more
site-pair duplets [document-origin, target]; one or other of these may
be a wild-card ("*");
* While the user is browsing a given site (top-level domain), and a DNT
header is to be sent to a target domain, if the duplet [top-level
domain, target domain] matches any duplet in the database, then a
DNT:0 header is sent, otherwise DNT:1 is sent.
Note
Note that a site may record no that it has previously asked for, and been
denied, an exception, if it wishes to avoid repeatedly asking the user for
an exception.
6.3.2 Exception use by browsers 6.3.2 Exception use by browsers
If a user wishes to be tracked by a tracker on this site, this should If a user agrees to allow tracking by a target on the top-level domain,
result in two user-agent behaviors: this should result in two user-agent behaviors:
1. If requests to the tracker for resources that are part of the DOM for 1. If requests to the target for resources that are part of the DOM for
pages on this site include a DNT header, that header must be DNT:OFF. pages on top-level domain include a DNT header, that header MUST be
DNT:0.
2. Responses to the JavaScript API indicated should be consistent with 2. Responses to the JavaScript API indicated should be consistent with
this user preference (see below). this user preference (see below).
Issue 159: How do we allow sites that mash-in ad-supported content to
maintain their own trusted third parties?
This model does not support mashed-up content which is in turn supported
by ads; it's not clear how to distinguish between embedded content which
is embedding ads (and hence the top-level domain stays the same) and
embedded content that should start a new context.
Proposal: For this version of the specification, we don't address this
corner case.
User-agents MUST handle each API request as a 'unit', granting and
maintaining it in its entirety, or not at all. That means that a
user-agent MUST NOT indicate to a site that a request for targets {a, b,
c} has been granted, and later remove only one or two of {a, b, c} from
its logical database of remembered grants. This assures sites that the set
of sites they need for operational integrity is treated as a unit. Each
separate call to an API is a separate unit.
When a user-agent receives an API request for an exception that already
exists (i.e. the grant is recorded in its database), it SHOULD bypass
asking the user to confirm, and simply re-confirm the grant to the caller.
Note
It is left up to individual user-agent implementations how to determine It is left up to individual user-agent implementations how to determine
and how and whether to store users' tracking preferences. and how and whether to store users' tracking preferences.
ISSUE-111: Different DNT values to signify existence of site-specific When an explicit list of domains is provided through the API, their names
might mean little to the user. The user might, for example, be told that
such-and-such top-level domain is asking for an exception for a specific
set of sites, rather than listing them by name; or the user-agent may
decide to ask the user for a site-wide exception, effectively ignoring the
list of domain names, if supplied.
Conversely, if a wild-card is used, the user may be told that the
top-level domain is asking for an exception for all third-parties that
are, or will be, embedded in it.
Issue 111: Different DNT values to signify existence of user-granted
exception exception
Should the user agent send a different DNT value to a first party site if
there exist site-specific exceptions for that first party? (e.g. DNT:2
implies "I have Do Not Track enabled but grant permissions to some third
parties while browsing this domain")
Proposal: No, this API provides client-side means for sites to request
that information. Sites may also employ cookies to recall a user's past
response.
6.4 JavaScript API for site-specific exceptions [POSTPONED] Should the user agent send a different DNT value to a first
party site if there exist user-granted exceptions for that first party?
(e.g. DNT:2 implies "I have Do Not Track enabled but grant permissions to
some third parties while browsing this domain")
Proposal: A previous proposal was that it can add itself to the list (i.e.
an exception for [site, site]) and then it will get DNT:0, but DNT:0 to a
first party means something different (that it can pass data to third
parties, and tracking is permitted). It would be better to have an
indication in the DNT header that one or more site-specific exceptions
exist for the given target (i.e. that there is at least one duplet in the
database with target as its first host name), for example "DNT:1E" where E
means you are a first party with one or more active exceptions.
6.4 JavaScript API for Site-specific Exceptions
6.4.1 API to request site-specific exceptions
[NoInterfaceObject] [NoInterfaceObject]
interface NavigatorDoNotTrack { interface NavigatorDoNotTrack {
void requestSiteSpecificTrackingException (sequence<DOMString> arrayOfDom void requestSiteSpecificTrackingException (
ainStrings, TrackingResponseCallback callback, optional siteName, optional e TrackingResponseCallback callback,
xplanationString, optional detailURI); optional sequence<DOMString> arrayOfDomainStrings,
optional optional siteName,
optional optional explanationString,
optional optional detailURI
);
}; };
6.4.1 Methods
requestSiteSpecificTrackingException requestSiteSpecificTrackingException
Called by a page to request or confirm a site-specific tracking Called by a page to request or confirm a user-granted tracking
exception. exception.
Parameter Type Nullable Optional Descripti on Parameter Type Nullable Optional Descripti on
arrayOfDomainStrings sequence<DOMString> * *
callback TrackingResponseCallback * * callback TrackingResponseCallback * *
siteName * * arrayOfDomainStrings sequence<DOMString> * *
explanationString * * siteName optional * *
detailURI * * explanationString optional * *
detailURI optional * *
Return type: void Return type: void
[Callback, NoInterfaceObject] [Callback, NoInterfaceObject]
interface TrackingResponseCallback { interface TrackingResponseCallback {
void handleEvent (boolean granted); void handleEvent (integer granted);
}; };
6.4.2 Methods
handleEvent handleEvent
The callback is called by the user agent to indicate the user's The callback is called by the user agent to indicate the user's
response. response.
Parameter Type Nullable Optional Description Parameter Type Nullable Optional Description
granted boolean * * granted integer * *
Return type: void Return type: void
The requestSiteSpecificTrackingException method takes two mandatory The requestSiteSpecificTrackingException method takes one mandatory
arguments: argument:
* arrayOfDomainStrings, a JavaScript array of strings, and
* callback, a method that will be called when the request is complete. * callback, a method that will be called when the request is complete.
It also takes three optional arguments: It also takes four optional arguments:
* siteName, a string for the name of this site, * arrayOfDomainStrings, a JavaScript array of strings,
* siteName, a user-readable string for the name of the top-level domain,
* explanationString, a short explanation of the request, and * explanationString, a short explanation of the request, and
* detailURI, a location at which further information about this request * detailURI, a location at which further information about this request
can be found. can be found.
Each string in arrayOfDomainStrings specifies a tracker. The special If the request does not include the arrayOfDomainStrings, then this
string "*" signifies all trackers. When called, request is for a site-wide exception. Otherwise each string in
requestSiteSpecificTrackingException must return immediately, then arrayOfDomainStrings specifies a target. When called,
asynchronously determine whether the user wants the requested exceptions. requestSiteSpecificTrackingException MUST return immediately, then
asynchronously determine whether the user grants the requested
exception(s).
The granted parameter passed to the callback is the user's response; true If the list arrayOfDomainStrings is supplied, the user-agent MAY choose to
indicates the user wants an exception on this site for all of the trackers ask the user to grant a site-wide exception. If it does so, and the user
specified in arrayOfDomainStrings. The response false indicates that the agrees, it MUST indicate this in the response callback.
user does not want an exception on this site for at least one of the
trackers specified in arrayOfDomainStrings. The execution of this API and the use of the resulting permission (if
granted) use the 'implicit' parameter, when the API is called, the
document origin. This forms the first part of the duplet in the logical
model, and hence in operation will be compared with the top-level domain.
The granted parameter passed to the callback is the user's response; The
response
* 0 indicates that user does not grant the exception on top-level domain
for the indicated targets.
* 1 indicates that the request was for specific targets and the the user
grants an exception on top-level domain for those specific targets.
* 2 indicates the user grants a site-wide exception on top-level domain
for all targets; the request may have been for specific targets or for
a site-wide exception.
If permission is granted for an explicit list, then the set of duplets
(one per target):
[document-origin, target]
is added to the database of remembered grants.
If permission is granted for a site-wide exception, then the duplets:
[document-origin, * ]
is added to the database of remembered grants.
A particular response to the API - like a DNT response header - is only A particular response to the API - like a DNT response header - is only
valid immediately, and users' preferences may change. valid immediately, and users' preferences may change.
A user agent may use an interactive method to ask the user about their A user agent MAY use an interactive method to ask the user about their
preferences, so sites should not assume that the callback function will be preferences, so sites SHOULD NOT assume that the callback function will be
called immediately. called immediately.
ISSUE-109: siteSpecificTrackingExceptions property has fingerprinting 6.4.2 API to Cancel a Site-specific Exception
risks: is it necessary?
[PENDING REVIEW] It has been removed from the proposal.
6.5 User interface guidelines [NoInterfaceObject]
interface NavigatorDoNotTrack {
boolean removeSiteSpecificTrackingException ();
};
removeSiteSpecificTrackingException
Ensures that the database of remembered grants no longer contains
any duplets for which the first part is the current document
origin; i.e., no duplets [document-origin, target] for any target.
There is no callback. After the call has been made, it is assured
that there are no site-specific or site-wide exceptions for the
given top-level-domain.
No parameters.
Return type: boolean
This returns a boolean indicating, when true, that the call has succeeded,
and that the database of grants no longer contains, or very soon will no
longer contain, the indicated grant(s); when false, some kind of
processing error occurred.
6.5 JavaScript API for Web-wide Exceptions
6.5.1 API to Request a Web-wide Exception
[NoInterfaceObject]
interface NavigatorDoNotTrack {
void requestWebWideTrackingException (
TrackingResponseCallback callback,
optional siteName,
optional optional explanationString,
optional optional detailURI
);
};
requestWebWideTrackingException
If permission is granted, then the single duplet [ * ,
document-origin] is added to the database of remembered grants.
The parameters are as described above in the request for
site-specific exceptions.
Parameter Type Nullable Optional Descripti
on
callback TrackingResponseCallback * *
siteName * *
explanationString optional * *
detailURI optional * *
Return type: void
Users may wish to configure exceptions for a certain trusted tracker
across all sites. This API requests the addition of a web-wide grant for a
specific site, to the database.
6.5.2 API to cancel a web-wide exception
[NoInterfaceObject]
interface NavigatorDoNotTrack {
boolean removeWebWideTrackingException ();
};
removeWebWideTrackingException
Ensures that the database of remembered grants no longer contains
the duplet [ * , document-origin]. There is no callback. After the
call has been made, the indicated pair is assured not to be in the
database. The same matching as is used for determining which
header to send is used to detect which entry (if any) to remove
from the database.
No parameters.
Return type: boolean
This returns a boolean indicating, when true, that the call has succeeded,
and that the database of grants no longer contains, or very soon will no
longer contain, the indicated grant; when false, some kind of processing
error occurred.
6.6 Querying a host's exception status
Issue 160: Do we need an exception-query API?
[PENDING REVIEW] It might be useful, and 'complete the model', if we had a
JS API that told a host what its current exception status is in a given
context. See proposal here.
Proposal: Specifically, an API QueryExceptionStatus() which examines the
document origin of the script, the current top-level domain and returns an
empty string if no DNT header would be sent to that document origin, or
the exact DNT header (DNT:1 or DNT:0) that would be sent otherwise.
[NoInterfaceObject]
interface NavigatorDoNotTrack {
DOMString requestDNTStatus ();
};
requestDNTStatus
Returns the same string value that would be sent in a
DNT-field-value (section 4.2 DNT Header Field for HTTP Requests)
to a target that is the document-origin of the request, in the
context of the current top-level domain. If no DNT header would be
sent (e.g. because a tracking preference is not enabled) the
return value is null.
No parameters.
Return type: DOMString
6.7 Transfer of an exception to another third party
A site may request an exception for one or more third party services used
in conjunction with its own offer. Those third party services may wish to
use other third parties to complete the request in a chain of
interactions. The first party will not necessarily know in advance whether
a known third party will use some other third parties.
If a user-agent sends a tracking exception to a given combination of
origin server and a named third party, the user agent will send DNT:0 to
that named third party. By receiving the DNT:0 header, the named third
party acquires the permission to track the user agent and collect the data
and process it in any way allowed by the legal system it is operating in.
Furthermore, the named third party receiving the DNT:0 header acquires at
least the right to collect data and process it for the given interaction
and any secondary use unless it receives a DNT:1 header from that
particular identified user agent.
The named third party is also allowed to transmit the collected data for
uses related to this interaction to its own sub-services and
sub-sub-services (transitive permission). The tracking permission request
triggered by the origin server is thus granted to the named third party
and its sub-services. This is even true for sub-services that would
normally receive a DNT:1 web-wide preference from the user-agent if the
user agent interacted with this service directly.
For advertisement networks this typically would mean that the collection
and auction system chain can use the data for that interaction and combine
it with existing profiles and data. The sub-services to the named third
party do not acquire an independent right to process the data for
independent secondary uses unless they, themselves, receive a DNT:0 header
from the user agent (as a result of their own request or the request of a
first-party). In our example of advertisement networks that means the
sub-services can use existing profiles in combination with the data
received, but they can not store the received information into a profile
until they have received a DNT:0 of their own.
A named third party acquiring an exception with this mechanism MUST make
sure that sub-services it uses acknowledge this constraint by requiring
the use of the appropriate tracking status value and qualifier, which is
"XX" (such as "tl"), from its sub-sub-services.
The permission acquired by the DNT mechanism does not override retention
limitations found in the legal system the content provider or the named
third party are operating in.
Issue 168: What is the correct way for sub-services to signal that they
are taking advantage of a transferred exception?
When the status values and qualifiers are fixed, the penultimate paragraph
will probably need adjusting to match. The use of "tl" (which meant
"tracking but only in accordance with local laws" when this text was
written) doesn't seem right, as the text talks, essentially, of the
sub-sub-service acting on behalf of the site that received the DNT:0
header, which might suggest something more like "CS" (service provision to
a third-party that received consent).
6.8 User interface guidelines
This section is non-normative. This section is non-normative.
User agents are free to implement exception management user interfaces as User agents are free to implement exception management user interfaces as
they see fit. Some agents might provide a prompt to the user at the time they see fit. Some agents might provide a prompt to the user at the time
of the request. Some agents might allow users to configure this preference of the request. Some agents might allow users to configure this preference
in advance. In either case, the user agent responds with the user's in advance. In either case, the user agent responds with the user's
preference. preference.
In general, it is expected that the site will explain, in its online
content, the need for an exception, and the consequences of granting or
denying an exception, to the user, and guide. The call to the API and the
resulting request for user confirmation should not be a 'surprise' to the
user, or require much explanation on the part of the user-agent.
A user agent that chooses to implement a prompt to present tracking A user agent that chooses to implement a prompt to present tracking
exception requests to the user might provide an interface like the exception requests to the user might provide an interface like the
following: following:
Example News (web.exnews.com) would like to know Example 10
whether you permit tracking by the following parties:
* exnews.analytico.net Example News (web.exnews.com) would like to confirm
* widgets.exsocial.org that you permit tracking by a specific set of sites (click
here for their names).
Example News says: Example News says:
"These sites allow Example News to see how we're These sites allow Example News to see how we're
doing, and provide useful features of the Example News doing, and provide useful features of the Example News
experience." [More info] experience. [More info]
[Allow Tracking] [Deny Tracking Request] [Allow Tracking] [Deny Tracking Request]
In this example, the domains listed are those specified in In this example, the domains listed are those specified in
arrayOfDomainStrings, the phrase "Example News" is from siteName, and the arrayOfDomainStrings, the phrase Example News is from siteName, and the
explanationString is displayed for the user with a "More info" link explanationString is displayed for the user with a More info link pointing
pointing to detailURI. to detailURI.
The user agent might then store that decision, and answer future requests The user agent might then store that decision, and answer future requests
based on this stored preference. User agents might provide users with based on this stored preference. A user agent might provide the user with
granular choice over which tracking origins are granted site-specific an interface to explicitly remove (or add) user-granted exceptions.
exceptions and which are not (using checkboxes, for example). User agents
might automatically clear site-specific exceptions after a period of time
or in response to user activity, like leaving a private browsing mode or
using a preference manager to edit their chosen exceptions. If a user
agent retains user preferences, it might provide the user with an
interface to explicitly add or remove site-specific exceptions.
Users might not configure their agents to have simple values for DNT, but Users might not configure their agents to have simple values for DNT, but
use different browsing modes or other contextual information to decide on use different browsing modes or other contextual information to decide on
a DNT value. What algorithm a user agent employs to determine DNT values a DNT value. What algorithm a user agent employs to determine DNT values
(or the lack thereof) is out of the scope of this specification. (or the lack thereof) is out of the scope of this specification.
In some user-agent implementations, decisions to grant exceptions may have In some user-agent implementations, decisions to grant exceptions may have
been made in the past (and since forgotten) or may have been made by other been made in the past (and since forgotten) or may have been made by other
users of the device. Thus, exceptions may not always represent the current users of the device. Thus, exceptions may not always represent the current
preferences of the user. Some user agents might choose to provide ambient preferences of the user. Some user agents might choose to provide ambient
notice that user-opted tracking is ongoing, or easy access to view and notice that user-opted tracking is ongoing, or easy access to view and
control these preferences. Users may desire options to edit exceptions control these preferences. Users may desire options to edit exceptions
either at the time of tracking or in a separate user interface. This might either at the time of tracking or in a separate user interface. This might
allow the user to edit their preferences for a site they do not trust allow the user to edit their preferences for a site they do not trust
without visiting that site. without visiting that site.
ISSUE: Should there be a normative requirement for the existence of a Issue 140: Do we need site-specific exceptions, i.e., concrete list of
revocation mechanism? (raised by npdoty) permitted third parties for a site?
6.6 Exceptions without a DNT header [PENDING REVIEW] In this section; yes, as some sites may have a mix of
trusted/needed third parties, and others that either don't need to track,
or aren't as trusted, or both. But all sites are (a) told what they got
granted (list, or *) and (b) are assured that requests will be treated
'atomically'.
6.9 Exceptions without a DNT header
Sites might wish to request exceptions even when a user arrives without a Sites might wish to request exceptions even when a user arrives without a
DNT header. Users might wish to grant affirmative permission to tracking DNT header. Users might wish to grant affirmative permission to tracking
on or by certain sites even without expressing general tracking on or by certain sites even without expressing general tracking
preferences. preferences.
User agents may instantiate User agents MAY instantiate
NavigatorDoNotTrack.requestSiteSpecificTrackingException even when NavigatorDoNotTrack.requestSiteSpecificTrackingException even when
navigator.doNotTrack is null. Sites should test for the existence of navigator.doNotTrack is null. Sites SHOULD test for the existence of
requestSiteSpecificTrackingException before calling the method. If an requestSiteSpecificTrackingException before calling the method. If an
exception is granted in this context and the user-agent stores that exception is granted in this context and the user-agent stores that
preference, a user agent may send a DNT:0 header even if a tracking preference, a user agent may send a DNT:0 header even if a tracking
preference isn't expressed for other requests. Persisted preferences may preference isn't expressed for other requests. Persisted preferences MAY
also affect which header is transmitted if a user later chooses to express also affect which header is transmitted if a user later chooses to express
a tracking preference. a tracking preference.
Note
Users might not configure their agents to have simple values for DNT, but Users might not configure their agents to have simple values for DNT, but
use different browsing modes or other contextual information to decide on use different browsing modes or other contextual information to decide on
a DNT value. What algorithm a user agent employs to determine DNT values a DNT value. What algorithm a user agent employs to determine DNT values
(or the lack thereof) is out of the scope of this specification. (or the lack thereof) is out of the scope of this specification.
6.7 Web-wide exceptions 6.10 Fingerprinting
Users may wish to configure exceptions for a certain trusted tracker
across several or all sites. User agent configuration of these preferences
is outside the scope of this specification.
ISSUE-113: Should there be a JavaScript API to prompt for a Web-wide
exception?
PROPOSAL: User agents can provide configuration options outside the scope
of this specification.
6.8 Fingerprinting
By storing a client-side configurable state and providing functionality to By storing a client-side configurable state and providing functionality to
learn about it later, this API might facilitate user fingerprinting and learn about it later, this API might facilitate user fingerprinting and
tracking. User agent developers ought to consider the possibility of tracking. User agent developers ought to consider the possibility of
fingerprinting during implementation and might consider rate-limiting fingerprinting during implementation and might consider rate-limiting
requests or using other heuristics to mitigate fingerprinting risk. User requests or using other heuristics to mitigate fingerprinting risk. User
agents should clear stored site-specific exceptions when the user chooses agents SHOULD clear stored user-granted exceptions when the user chooses
to clear cookies or other client-side state. to clear cookies or other client-side state.
ISSUE-114: Guidance or mitigation of fingerprinting risk for
user-agent-managed site-specific tracking exceptions
PENDING REVIEW Above text provides guidance for user agent developers.
A. Acknowledgements A. Acknowledgements
This specification consists of input from many discussions within and This specification consists of input from many discussions within and
around the W3C Tracking Protection Working Group, along with written around the W3C Tracking Protection Working Group, along with written
contributions from Nick Doty (W3C/MIT), Roy T. Fielding (Adobe), Tom contributions from Nick Doty (W3C/MIT), Rob van Eijk (Invited Expert),
Lowenthal (Mozilla), Aleecia M. McDonald (Mozilla), Matthias Schunter Roy T. Fielding (Adobe), Tom Lowenthal (Mozilla), Jonathan Mayer
(IBM), John Simpson (Consumer Watchdog), David Singer (Apple), Shane Wiley (Stanford), Aleecia M. McDonald (Mozilla), Matthias Schunter (IBM),
John Simpson (Consumer Watchdog), David Singer (Apple), David Wainberg
(Network Advertising Initiative), Rigo Wenning (W3C/ERCIM), Shane Wiley
(Yahoo!), and Andy Zeigler (Microsoft). (Yahoo!), and Andy Zeigler (Microsoft).
The DNT header field is based on the original Do Not Track submission by The DNT header field is based on the original Do Not Track submission by
Jonathan Mayer (Stanford), Arvind Narayanan (Stanford), and Sid Stamm Jonathan Mayer (Stanford), Arvind Narayanan (Stanford), and Sid Stamm
(Mozilla). The DOM API for NavigatorDoNotTrack is based on the Web (Mozilla). The DOM API for NavigatorDoNotTrack is based on the Web
Tracking Protection submission by Andy Zeigler, Adrian Bateman, and Eliot Tracking Protection submission by Andy Zeigler, Adrian Bateman, and
Graff (Microsoft). Many thanks to Robin Berjon for ReSpec.js. Eliot Graff (Microsoft). Many thanks to Robin Berjon for ReSpec.js.
B. References B. References
B.1 Normative references B.1 Normative references
[ABNF] [ABNF]
D. Crocker and P. Overell. Augmented BNF for Syntax D. Crocker and P. Overell. Augmented BNF for Syntax
Specifications: ABNF. January 2008. Internet RFC 5234. URL: Specifications: ABNF. January 2008. Internet RFC 5234. URL:
http://www.ietf.org/rfc/rfc5234.txt http://www.ietf.org/rfc/rfc5234.txt
[HTTP11] [HTTP11]
R. Fielding; et al. Hypertext Transfer Protocol - HTTP/1.1. June R. Fielding; et al. Hypertext Transfer Protocol - HTTP/1.1. June
1999. Internet RFC 2616. URL: http://www.ietf.org/rfc/rfc2616.txt 1999. Internet RFC 2616. URL: http://www.ietf.org/rfc/rfc2616.txt
[NAVIGATOR] [NAVIGATOR]
Ian Hickson, David Hyatt. Navigator interface in HTML5. 15 April Robin Berjon; Travis Leithead; Silvia Pfeiffer; Erika Doyle
2011. Editors' draft. (Work in progress.) URL: Navara; Edward O'Connor; Ian Hickson. The Navigator object -
http://dev.w3.org/html5/spec/timers.html#navigator System state and capabilities - HTML5. 28 September 2012. Editors'
draft. (Work in progress.) URL:
http://dev.w3.org/html5/spec/system-state-and-capabilities.html#the
-navigator-object
[RFC2119] [RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels. March 1997. Internet RFC 2119. URL: Levels. March 1997. Internet RFC 2119. URL:
http://www.ietf.org/rfc/rfc2119.txt http://www.ietf.org/rfc/rfc2119.txt
[RFC4627] [RFC4627]
D. Crockford. The application/json Media Type for JavaScript D. Crockford. The application/json Media Type for JavaScript
Object Notation (JSON) July 2006. Internet RFC 4627. URL: Object Notation (JSON) July 2006. Internet RFC 4627. URL:
http://www.ietf.org/rfc/rfc4627.txt http://www.ietf.org/rfc/rfc4627.txt
[TRACKING-COMPLIANCE] [TRACKING-COMPLIANCE]
Justin Brookman; Sean Harvey; Erica Newland; Heather West. Justin Brookman; Sean Harvey; Erica Newland; Heather West.
Tracking Compliance and Scope. 13 March 2012. W3C Working Draft. Tracking Compliance and Scope. 2 October 2012. W3C Working Draft.
(Work in progress.) URL: (Work in progress.) URL:
http://www.w3.org/TR/2012/WD-tracking-compliance-20120313/ http://www.w3.org/TR/2012/WD-tracking-compliance-20121002/
[WEBIDL] [WEBIDL]
Cameron McCormack. Web IDL. 27 September 2011. W3C Working Draft. Cameron McCormack. Web IDL. 27 September 2011. W3C Working Draft.
(Work in progress.) URL: (Work in progress.) URL:
http://www.w3.org/TR/2011/WD-WebIDL-20110927/ http://www.w3.org/TR/2011/WD-WebIDL-20110927/
B.2 Informative references B.2 Informative references
[COOKIES] [COOKIES]
Adam Barth. HTTP State Management Mechanism. April 2011. Internet Adam Barth. HTTP State Management Mechanism. April 2011. Internet
Proposed Standard RFC 6265. URL: Proposed Standard RFC 6265. URL:
http://www.rfc-editor.org/rfc/rfc6265.txt http://www.rfc-editor.org/rfc/rfc6265.txt
[KnowPrivacy] [KnowPrivacy]
Joshua Gomez; Travis Pinnick; Ashkan Soltani. KnowPrivacy. 1 June Joshua Gomez; Travis Pinnick; Ashkan Soltani. KnowPrivacy. 1 June
2009. URL: 2009. URL:
http://www.knowprivacy.org/report/KnowPrivacy_Final_Report.pdf http://www.knowprivacy.org/report/KnowPrivacy_Final_Report.pdf
[RFC3986]
T. Berners-Lee; R. Fielding; L. Masinter. Uniform Resource
Identifier (URI): Generic Syntax. January 2005. Internet RFC 3986.
URL: http://www.ietf.org/rfc/rfc3986.txt
[RFC5785] [RFC5785]
Mark Nottingham; Eran Hammer-Lahav. Defining Well-Known Uniform Mark Nottingham; Eran Hammer-Lahav. Defining Well-Known Uniform
Resource Identifiers (URIs). April 2010. Internet Proposed Resource Identifiers (URIs). April 2010. Internet Proposed
Standard RFC 5785. URL: http://www.rfc-editor.org/rfc/rfc5785.txt Standard RFC 5785. URL: http://www.rfc-editor.org/rfc/rfc5785.txt
[URI-TEMPLATE] [URI-TEMPLATE]
Joe Gregorio; Roy T. Fielding; Marc Hadley; Mark Nottingham; David Joe Gregorio; Roy T. Fielding; Marc Hadley; Mark Nottingham; David
Orchard. URI Template. 26 January 2012. Internet Draft (work in Orchard. URI Template. March 2012. Internet RFC 6570. URL:
progress). URL: http://www.rfc-editor.org/rfc/rfc6570.txt
http://tools.ietf.org/html/draft-gregorio-uritemplate-08
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