12 IANA considerations

12.1 text/html

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
text
Subtype name:
html
Required parameters:
No required parameters
Optional parameters:
charset

The charset parameter may be provided to definitively specify the document's character encoding, overriding any character encoding declarations in the document. The parameter's value must be the name of the character encoding used to serialize the file, must be a valid character encoding name, and must be an ASCII case-insensitive match for the preferred MIME name for that encoding. [IANACHARSET]

Encoding considerations:
8bit (see the section on character encoding declarations)
Security considerations:

Entire novels have been written about the security considerations that apply to HTML documents. Many are listed in this document, to which the reader is referred for more details. Some general concerns bear mentioning here, however:

HTML is scripted language, and has a large number of APIs (some of which are described in this document). Script can expose the user to potential risks of information leakage, credential leakage, cross-site scripting attacks, cross-site request forgeries, and a host of other problems. While the designs in this specification are intended to be safe if implemented correctly, a full implementation is a massive undertaking and, as with any software, user agents are likely to have security bugs.

Even without scripting, there are specific features in HTML which, for historical reasons, are required for broad compatibility with legacy content but that expose the user to unfortunate security problems. In particular, the img element can be used in conjunction with some other features as a way to effect a port scan from the user's location on the Internet. This can expose local network topologies that the attacker would otherwise not be able to determine.

HTML relies on a compartmentalization scheme sometimes known as the same-origin policy. An origin in most cases consists of all the pages served from the same host, on the same port, using the same protocol.

It is critical, therefore, to ensure that any untrusted content that forms part of a site be hosted on a different origin than any sensitive content on that site. Untrusted content can easily spoof any other page on the same origin, read data from that origin, cause scripts in that origin to execute, submit forms to and from that origin even if they are protected from cross-site request forgery attacks by unique tokens, and make use of any third-party resources exposed to or rights granted to that origin.

Interoperability considerations:
Rules for processing both conforming and non-conforming content are defined in this specification.
Published specification:
This document is the relevant specification. Labeling a resource with the text/html type asserts that the resource is an HTML document using the HTML syntax.
Applications that use this media type:
Web browsers, tools for processing Web content, HTML authoring tools, search engines, validators.
Additional information:
Magic number(s):
No sequence of bytes can uniquely identify an HTML document. More information on detecting HTML documents is available in the Media Type Sniffing specification. [MIMESNIFF]
File extension(s):
"html" and "htm" are commonly, but certainly not exclusively, used as the extension for HTML documents.
Macintosh file type code(s):
TEXT
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with text/html resources either refer to the indicated part of the document or provide state information for in-page scripts.

12.2 multipart/x-mixed-replace

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
multipart
Subtype name:
x-mixed-replace
Required parameters:
Optional parameters:
No optional parameters.
Encoding considerations:
binary
Security considerations:
Subresources of a multipart/x-mixed-replace resource can be of any type, including types with non-trivial security implications such as text/html.
Interoperability considerations:
None.
Published specification:
This specification describes processing rules for Web browsers. Conformance requirements for generating resources with this type are the same as for multipart/mixed. [RFC2046]
Applications that use this media type:
This type is intended to be used in resources generated by Web servers, for consumption by Web browsers.
Additional information:
Magic number(s):
No sequence of bytes can uniquely identify a multipart/x-mixed-replace resource.
File extension(s):
No specific file extensions are recommended for this type.
Macintosh file type code(s):
No specific Macintosh file type codes are recommended for this type.
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with multipart/x-mixed-replace resources apply to each body part as defined by the type used by that body part.

12.3 application/xhtml+xml

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
application
Subtype name:
xhtml+xml
Required parameters:
Same as for application/xml [RFC3023]
Optional parameters:
Same as for application/xml [RFC3023]
Encoding considerations:
Same as for application/xml [RFC3023]
Security considerations:
Same as for application/xml [RFC3023]
Interoperability considerations:
Same as for application/xml [RFC3023]
Published specification:
Labeling a resource with the application/xhtml+xml type asserts that the resource is an XML document that likely has a root element from the HTML namespace. Thus, the relevant specifications are the XML specification, the Namespaces in XML specification, and this specification. [XML] [XMLNS]
Applications that use this media type:
Same as for application/xml [RFC3023]
Additional information:
Magic number(s):
Same as for application/xml [RFC3023]
File extension(s):
"xhtml" and "xht" are sometimes used as extensions for XML resources that have a root element from the HTML namespace.
Macintosh file type code(s):
TEXT
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with application/xhtml+xml resources have the same semantics as with any XML MIME type. [RFC3023]

12.4 application/x-www-form-urlencoded

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
application
Subtype name:
x-www-form-urlencoded
Required parameters:
No parameters
Optional parameters:
No parameters
Encoding considerations:
7bit (US-ASCII encoding of octets that themselves can be encoding text using any ASCII-compatible character encoding)
Security considerations:

In isolation, an application/x-www-form-urlencoded payload poses no security risks. However, as this type is usually used as part of a form submission, all the risks that apply to HTML forms need to be considered in the context of this type.

Interoperability considerations:
Rules for generating and processing application/x-www-form-urlencoded payloads are defined in this specification.
Published specification:
This document is the relevant specification. Algorithms for encoding and decoding are defined.
Applications that use this media type:
Web browsers and servers.
Additional information:
Magic number(s):
There is no reliable mechanism for recognising application/x-www-form-urlencoded payloads.
File extension(s):
Not applicable.
Macintosh file type code(s):
Not applicable.
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
This type is only intended to be used to describe HTML form submission payloads.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers have no meaning with the application/x-www-form-urlencoded type.

12.5 text/cache-manifest

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
text
Subtype name:
cache-manifest
Required parameters:
No parameters
Optional parameters:
No parameters
Encoding considerations:
8bit (always UTF-8)
Security considerations:

Cache manifests themselves pose no immediate risk unless sensitive information is included within the manifest. Implementations, however, are required to follow specific rules when populating a cache based on a cache manifest, to ensure that certain origin-based restrictions are honored. Failure to correctly implement these rules can result in information leakage, cross-site scripting attacks, and the like.

Interoperability considerations:
Rules for processing both conforming and non-conforming content are defined in this specification.
Published specification:
This document is the relevant specification.
Applications that use this media type:
Web browsers.
Additional information:
Magic number(s):
Cache manifests begin with the string "CACHE MANIFEST", followed by either a U+0020 SPACE character, a "tab" (U+0009) character, a "LF" (U+000A) character, or a "CR" (U+000D) character.
File extension(s):
"appcache"
Macintosh file type code(s):
No specific Macintosh file type codes are recommended for this type.
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers have no meaning with text/cache-manifest resources.

12.6 Ping-To

This section describes a header field for registration in the Permanent Message Header Field Registry. [RFC3864]

Header field name:
Ping-To
Applicable protocol:
http
Status:
standard
Author/Change controller:
W3C
Specification document(s):
This document is the relevant specification.
Related information:
None.

12.7 web+ scheme prefix

This section describes a convention for use with the IANA URI scheme registry. It does not itself register a specific scheme. [RFC4395]

Schemes using the web+ prefix must have names starting with the four characters "web+" followed by one or more letters in the range a-z.

Registrations of such schemes should specify the syntax and semantics of the scheme. Registrations should define what applications and/or protocols use the scheme.

All "web+" schemes should use UTF-8 encodings were relevant.

Any Web page is able to register a handler for all "web+" schemes. As such, these schemes must not be used for features intended to be core platform features (e.g. network transfer protocols like HTTP or FTP). Similarly, such schemes must not store confidential information in their URLs, such as usernames, passwords, personal information, or confidential project names.

Registrations should reference the description of web+ schemes in Custom scheme and content handlers, HTML5.