Copyright © 2021 W3C® (MIT, ERCIM, Keio, Beihang). W3C liability, trademark and permissive document license rules apply.
[SMIL3] This specification defines a JSON-based file format that provides developers with a centralized place to put metadata associated with a web application. This metadata includes, but is not limited to, the web application's name, links to icons, as well as the preferred URL to open when a user launches the web application. The manifest also allows developers to declare a default screen orientation for their web application, as well as providing the ability to set the display mode for the application (e.g., in fullscreen). Additionally, the manifest allows a developer to "scope" a web application to a URL. This restricts the URLs to which the manifest is applied and provides a means to "deep link" into a web application from other applications.
Using this metadata, user agents can provide developers with means to create user experiences that are more comparable to that of a native application.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
Implementors need to be aware that this specification is not stable. However, aspects of this specification are shipping in at least one browser (see links to implementation status at the top of this document). Implementors who are not taking part in the discussions will find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation phase should subscribe to the repository on GitHub and take part in the discussions.
This document was published by the Web Applications Working Group as a Working Draft. This document is intended to become a W3C Recommendation.
GitHub Issues are preferred for discussion of this specification.
Publication as a Working Draft does not imply endorsement by the W3C 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 document as other than work in progress.
This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This document is governed by the 15 September 2020 W3C Process Document.
This section is non-normative.
This section shows how developers can make use of the various features of this specification.
This section is non-normative.
The following shows a very simple manifest.
{
"name": "Donate App",
"description": "This app helps you donate to worthy causes.",
"icons": [{
"src": "images/icon.png",
"sizes": "192x192"
}]
}
The following shows a more typical manifest.
{
"lang": "en",
"dir": "ltr",
"name": "Super Racer 3000",
"short_name": "Racer3K",
"icons": [{
"src": "icon/lowres.webp",
"sizes": "64x64",
"type": "image/webp"
},{
"src": "icon/lowres.png",
"sizes": "64x64"
}, {
"src": "icon/hd_hi",
"sizes": "128x128"
}],
"scope": "/racer/",
"start_url": "/racer/start.html",
"display": "fullscreen",
"orientation": "landscape",
"theme_color": "aliceblue",
"background_color": "red"
}
link
element to link to a manifest
This section is non-normative.
The example also shows how to use the link type "manifest" and
how to use other meta
and link
elements to give the web
application a fallback name and set of icons.
<!doctype>
<html>
<title>Racer 3K</title>
<!-- Startup configuration -->
<link rel="manifest" href="manifest.webmanifest">
<!-- Fallback application metadata for legacy browsers -->
<meta name="application-name" content="Racer3K">
<link rel="icon" sizes="16x16 32x32 48x48" href="lo_def.ico">
<link rel="icon" sizes="512x512" href="hi_def.png">
.webmanifest
. Some
web servers recognize this extension and transfer the file using the
standardized application manifest MIME type
(application/manifest+json
). Developers can also choose a
different extension (e.g. .json
) or none at all (e.g.
/api/GetManifest
), but are encouraged to transfer the manifest
using the application/manifest+json
MIME type, although any
JSON MIME type is ok.
A common use case of a manifest is for a user agent to install a web application; whereby the user agent provides the end-user with a means of instantiating a new top-level browsing context that has the manifest's members applied to it. A web application that is installed is known as a installed web application. That is, the manifest's members, or their defaults, are in effect on the top-level browsing context. This distinguishes an installed web application from a traditional bookmark, as opening a web page from a traditional bookmark will not have the manifest's properties applied to it.
For example, on user agents that support installation, a web application could be presented and launched in a way that, to the end-user, is indistinguishable from native applications: such as appearing as a labeled icon on the home screen, launcher, or start menu. When launched, the manifest is applied by the user agent to the top-level browsing context prior to the start URL being loaded. This gives the user agent an opportunity to apply the relevant values of the manifest, possibly changing the display mode and screen orientation of the web application. Alternatively, and again as an example, the user agent could install the web application into a list of bookmarks within the user agent itself.
A document is installable if it's a top-level browsing context and the user agent deems it to be installable (e.g., see § 2.4 Installability signals ).
The application's name is derived from either the
name
member or short_name
member (if either is present)
- otherwise, it is generated by the user agent or provided by the
end-user.
When either member is missing from the manifest, a user agent MAY use
the name
member as a fallback for the short_name
member
or vice versa.
If the name
and short_name
members are undefined, the
user agent SHOULD assign a default name (e.g., "Untitled") that
follows platform conventions. Alternatively, a user agent MAY allow
the end-user to input some text that can serve as the
application's name.
When both the name
and short_name
members are present,
it is left up to implementations to decide which member is best
suited for the space available (e.g., the short_name
member
might be better suited for the space available underneath an icon).
It is RECOMMENDED that UI that affords the end user the ability to install a web application also allows inspecting the icon, name, start URL, origin, etc. pertaining to a web application. This is to give an end-user an opportunity to make a conscious decision to approve, and possibly modify, the information pertaining to the web application before installing it. This also gives the end-user an opportunity to discern if the web application is spoofing another web application, by, for example, using an unexpected icon or name.
It is RECOMMENDED that user agents prevent other applications from determining which applications are installed on the system (e.g., via a timing attack on the user agent's cache). This could be done by, for example, invalidating from the user agent's cache the resources linked to from the manifest (for example, icons) after a web application is installed - or by using an entirely different cache from that used for regular web browsing.
This section is non-normative.
By design, this specification does not provide developers with an explicit API to "install" a web application. Instead, a manifest can serve as an installability signal to a user agent that a web application can be installed.
Examples of installability signals for a web application:
name
member and a
suitable icon (e.g., of a particular format and of a minimum
width/height).
This list is not exhaustive and some installability signals might not apply to all user agents. How a user agent makes use of these installability signals to determine if a web application can be installed is left to implementers.
User agents SHOULD provide a mechanism for the user to remove an installed web application application.
It is RECOMMENDED that at the time of removal, the user agent also present the user with an opportunity to revoke other persistent data and settings associated with the application, such as permissions and persistent storage.
A display mode represents how the web application is being presented within the context of an OS (e.g., in fullscreen, etc.). Display modes correspond to user interface (UI) metaphors and functionality in use on a given platform. The UI conventions of the display modes are purely advisory and implementers are free to interpret them how they best see fit.
Once a user agent applies a particular display mode to an application context, it becomes the default display mode for the top-level browsing context (i.e., it is used as the display mode when the window is navigated). The user agent MAY override the default display mode for security reasons (e.g., the top-level browsing context is navigated to another origin) and/or the user agent MAY provide the user with a means of switching to another display mode.
When the display
member is
missing, or if there is no valid display
member, the user agent uses the
browser
display mode as the default display mode.
As such, the user agent MUST support the browser
display
mode.
Each display mode, except browser
, has a
fallback display mode, which is the display mode that
the user agent can try to use if it doesn't support a particular
display mode. If the user agent does support a fallback
display mode, then it checks to see if it can use that display
mode's fallback display mode. This creates a fallback chain,
with the default display mode (browser
) being the
last item in the chain.
For example, SuperSecure Browser (a fictitious browser) only supports
the minimal-ui
and browser
display modes,
but a developer declares that she wants fullscreen
in
the manifest. In this case, the user agent will first check if it
supports fullscreen
(it doesn't), so it falls back to
standalone
(which it also doesn't support), and
ultimately falls back to minimal-ui
.
The display modes values defined by
DisplayModeType
, and their corresponding fallback display
modes are as follows:
fullscreen
fullscreen
is
standalone
.
standalone
standalone
is
minimal-ui
.
minimal-ui
standalone
, but provides the end-user
with some means to access a minimal set of UI elements for
controlling navigation (i.e., back, forward, reload, and perhaps some
way of viewing the document's address). A user agent can include
other platform specific UI elements, such as "share" and "print"
buttons or whatever is customary on the platform and user agent.
minimal-ui
is
browser
.
browser
browser
display mode doesn't have a
fallback display mode (conforming user agents are required to
support the browser
display mode).
The fullscreen
display mode is orthogonal to, and works
independently of, the Fullscreen API Standard. The fullscreen
display mode affects the fullscreen state of the browser window,
while the [FULLSCREEN] API operates on an element contained within
the viewport. As such, a web application can have its display
mode set to fullscreen
, while
document.fullScreenElement
returns null
, and
fullscreenEnabled
returns false
.
When the web application is running, it is RECOMMENDED that the user agent provides the end-user a means to access common information about the web application, such as the origin, start and/or current URL, granted permissions, and associated icon. How such information is exposed to end-users is left up to implementers.
Additionally, when applying a manifest that sets the display
mode to anything except "browser
", it is RECOMMENDED that
the user agent clearly indicate to the end-user that their are
leaving the normal browsing context of a web browser. Ideally,
launching or switching to a web application is performed in a manner
that is consistent with launching or switching to other applications
in the host platform. For example, a long and obvious animated
transition, or speaking the text "Launching application X".
'display-mode'
media feature
The display-mode
media feature represents,
via a CSS media query [MEDIAQ], the display mode of the web
application. This media feature applies to the top-level browsing
context and any child browsing contexts. Child browsing contexts
reflect the display mode of the top-level browsing
context.
A user agent MUST expose the 'display-mode
' media
feature irrespective of whether a manifest is being applied to a
browsing context. For example, if the end-user puts the whole user
agent into fullscreen, then the user agent would reflect this change
to CSS and scripts via the 'display-mode
' media feature.
Please note that the fullscreen
display mode is
not directly related to the CSS :fullscreen
pseudo-class specified in the Fullscreen API Standard. The
:fullscreen
pseudo-class matches exclusively when a
[HTML] element is put into the fullscreen element stack. However,
a side effect of calling the requestFullscreen()
method on an element using the [FULLSCREEN] API is that the
browser window can enter a fullscreen mode at the OS-level. In such
a case, both :fullscreen
and (display-mode:
fullscreen)
will match.
On some platforms, it is possible for a user to put a browser
window into fullscreen without the aid of the Fullscreen API Standard.
When this happens, the :fullscreen
pseudo class will
not match, but (display-mode: fullscreen)
will match.
This is exemplified in CSS code below.
/* applies when the window is fullscreen */
@media all and (display-mode: fullscreen) {
...
}
/* applies when an element goes fullscreen */
#game:fullscreen {
...
}
fullscreen
| standalone
| minimal-ui
|
browser
A user agent MUST reflect the applied display mode of the web application via a CSS media query [MEDIAQ].
An example in CSS:
@media all and (display-mode: minimal-ui) {
/* ... */
}
@media all and (display-mode: standalone) {
/* ... */
}
Accessing the display-mode media feature in ECMAScript through
matchMedia()
of [CSSOM-VIEW]:
const standalone = matchMedia( '(display-mode: standalone)' );
standalone.onchange = (e) => {
/* handle changes to display mode */
}
if (standalone.matches) {
/* do standalone things */
}
The 'display-mode'
media feature allows an origin
access to aspects of a user’s local computing environment and,
together with the display
member, allows an origin
some measure of control over a user agent’s native UI: Through a
CSS media query, a script can know the display mode of a web
application. An attacker could, in such a case, exploit the fact
that an application is being displayed in fullscreen to mimic the
user interface of another application.
This section defines algorithms for processing a manifest, and applying a manifest.
A user agent MUST support the link type "manifest" and the associated steps for how to fetch and process the linked resource.
When instructed to issue a developer warning, the user agent MAY report the conformance violation to the developer in a user-agent-specific manner (e.g., report the problem in an error console), or MAY ignore the error and do nothing.
When instructed to ignore, the user agent MUST act as if whatever manifest, member, or value caused the condition is absent.
The following algorithm provides an extension point: other specifications that add new members to the manifest are encouraged to hook themselves into this specification at this point in the algorithm. They SHOULD NOT modify the existing values already in the manifest object.
The extension point is meant to help avoid issues related to monkey patching.
The steps for processing a manifest are
given by the following algorithm. The algorithm takes link
el and a Response response.
"{}"
).
"{}"
).
start_url
"] to the result of
running processing the start_url
member given
json["start_url
"], manifest URL, and
document URL.
lang
"] to the result of running
processing the lang
member given
json["lang
"].
scope
"] to the result of running
processing the scope
member given
json["scope
"], manifest URL, and
manifest["start_url
"].
theme_color
"] to the result of
running processing a color member given
manifest["theme_color
"].
background_color
"] to the result
of running processing a color member given
json["background_color
"].
icons
"] to the result of running
processing ManifestImageResource
members given
json["icons
"] and manifest URL.
related_applications
"] to the
result of running processing the related_applications
member given json["related_applications
"].
shortcuts
member with
manifest URL and manifest.
A processed manifest is applied to a top-level browsing context, meaning that the members of the processed manifest are affecting the presentation or behavior of a browsing context.
A top-level browsing context that has a manifest applied to it is referred to as an application context.
If an application context is created as a result of the user
agent being asked to navigate to a deep link, the user
agent MUST immediately navigate to the deep link with
historyHandling set to "replace
". Otherwise, when the
application context is created, the user agent MUST
immediately navigate to the start URL with
historyHandling set to "replace
".
The appropriate time to apply a manifest is when the application context is created and before navigation to the start URL begins.
Is there a reason that the spec only defines a declarative way to request that a user agent obtain and process a manifest?
Likewise, it would be useful to have an explicit way to request that the user-agent update it's version of the manifest.
The steps for processing a color member are given by the
following algorithm. The algorithm takes a USVString
potential color as an argument. This algorithm returns a
USVString
or undefined
.
undefined
.
undefined
.
Only sRGB colors, and colors the user agent can convert to sRGB
without any outside knowledge, are supported. For example, lab(…)
or
color(display-p3, …)
can be converted to sRGB without outside
knowledge, but color(--custom-profile, …)
would require finding a
matching "@color-profile" rule which cannot be specified in the
manifest.
WebAppManifest
dictionary
WebIDLdictionaryWebAppManifest
{TextDirectionType
dir
= "auto"; DOMStringlang
; USVStringname
; USVStringshort_name
; sequence<ManifestImageResource
>icons
; USVStringstart_url
;DisplayModeType
display
= "browser"; OrientationLockTypeorientation
; USVStringtheme_color
; USVStringbackground_color
; USVStringscope
; sequence<ShortcutItem
>shortcuts
; };
A manifest is a JSON document that contains startup parameters and application defaults for when a web application is launched.
Every manifest has an associated manifest URL, which is the [URL] from which the manifest was fetched.
dir
member
WebIDLenumTextDirectionType
{ "ltr
", "rtl
", "auto
" };
The dir
member specifies the base direction for
the localizable members of the manifest. The dir
member's value can be set to one of the text-direction values.
The localizable members are:
name
member.
short_name
member.
ShortcutItem
's name
member.
ShortcutItem
's short_name
member.
ShortcutItem
's description
member.
The text-direction values
defined by TextDirectionType
, are the following, implying
that the value of the localizable members is by default:
ltr
rtl
auto
When displaying the localizable members to an end-user, if the
base direction is ltr
or rtl
:
ltr
, or 1 if the base direction
is rtl
.
ltr
, or a right-to-left embedding
if the base direction is rtl
.
lang
member
The lang
member is a language tag (string)
that specifies the primary language for the values of the manifest's
localizable members (as knowing the language can also help
with directionality).
A language tag is a string that matches the
production of a Language-Tag
defined in the [BCP47]
specifications (see the IANA
Language Subtag Registry for an authoritative list of possible
values). That is, a language range is composed of one or more
subtags that are delimited by a U+002D HYPHEN-MINUS ("-").
For example, the 'en-AU
' language range represents
English as spoken in Australia, and 'fr-CA
' represents
French as spoken in Canada. Language tags that meet the validity
criteria of [RFC5646] section 2.2.9 that can be verified without
reference to the IANA Language Subtag Registry are considered
structurally valid.
The steps for processing the lang
member is
given by the following algorithm. The algorithm takes a
WebAppManifest
manifest as an argument. This
algorithm returns a DOMString?
.
false
,
then:
undefined
.
undefined
name
member
The name
member is a string that represents the
name of the web application as it is usually displayed to the user
(e.g., amongst a list of other applications, or as a label for an
icon).
The
member serves as the accessible name of an
installed web application.
name
short_name
member
The short_name
member is a string that represents a
short version of the name of the web application. It is intended to
be used where there is insufficient space to display the full name of
the web application.
scope
member
People are confused by the lack of examples relating to scope:
pwa-builder/PWABuilder-CLI#42 (comment)
The scope
member is a string that represents the
navigation scope of this web application's
application context.
The steps for processing the scope
member is
given by the following algorithm. The algorithm takes a
USVString value, a URL manifest
URL, and a URL start URL. This algorithm returns a
URL.
scope
is omitted or an error) is
the start URL, with its filename, query, and fragment
removed.
icons
member
The icons
member are images that serve as iconic
representations of the web application in various contexts. For
example, they can be used to represent the web application amongst a
list of other applications, or to integrate the web application with
an OS's task switcher and/or
system preferences.
If there are multiple equally appropriate images in
, a user agent MUST use the last one declared
in order at the time that the user agent collected the list of
icons
. If the user agent tries to use an icon but
that icon is determined, upon closer examination, to in fact be
inappropriate (e.g. because its content type is unsupported), then
the user agent MUST try the next-most-appropriate icon as determined
by examining the icons
's members.
ManifestImageResource
In the following example, the developer has made the following choices about the icons associated with the web application:
type
member. If the user agent doesn't support WebP,
it falls back to the second icon of the same size. The MIME
type of this icon can then be either determined via a HTTP
header, or can be sniffed by
the user agent once the first few bytes of the icon are received.
{
"icons": [
{
"src": "icon/lowres.webp",
"sizes": "48x48",
"type": "image/webp"
},{
"src": "icon/lowres",
"sizes": "48x48"
},{
"src": "icon/hd_hi.ico",
"sizes": "72x72 96x96 128x128 256x256"
},{
"src": "icon/hd_hi.svg",
"sizes": "257x257"
}]
}
display
member
WebIDLenumDisplayModeType
{ "fullscreen
", "standalone
", "minimal-ui
", "browser
" };
The display
member is a DisplayModeType
, whose
value is one of display modes values. The item represents the
developer's preferred display mode for the web application.
orientation
member
The orientation
member is a string that serves as
the default screen orientation for all top-level browsing
contexts of the web application. The possible values are those of
the OrientationLockType
enum defined in [SCREEN-ORIENTATION].
If the user agent honors the value of the orientation
member
as the default screen orientation, then that serves as the
default screen orientation for the life of the web application
(unless overridden by some other means at runtime). This means that
the user agent MUST return the orientation to the default screen
orientation any time the orientation is unlocked
[SCREEN-ORIENTATION] or the top-level browsing context is
navigated.
Although the specification relies on the [SCREEN-ORIENTATION]'s
OrientationLockType
, it is OPTIONAL for a user agent to implement
the [SCREEN-ORIENTATION] API. Supporting the [SCREEN-ORIENTATION]
API is, of course, RECOMMENDED.
Certain UI/UX concerns and/or platform conventions will mean that
some screen orientations and display modes cannot be used
together. Which orientations and display modes cannot be used
together is left to the discretion of implementers. For example, for
some user agents, it might not make sense to change the default
screen orientation of an application while in
browser
display mode.
Once the web application is running, other means can change the orientation of a top-level browsing context (such as via [SCREEN-ORIENTATION] API).
start_url
member
The start_url
member is a string that represents
the start URL , which is URL that the developer
would prefer the user agent load when the user launches the web
application (e.g., when the user clicks on the icon of the web
application from a device's application menu or homescreen).
The start_url
member is purely advisory, and a user agent MAY
ignore it or provide the end-user the choice not to make use
of it. A user agent MAY also allow the end-user to modify the URL
when, for instance, a bookmark for the web application is being
created or any time thereafter.
The steps for processing the start_url
member
are given by the following algorithm. The algorithm takes a
USVString value, a URL manifest
URL, and a URL document URL. This algorithm
returns a URL.
start_url
needs to be same origin as the Document
of
the top-level browsing context.
For example, if the value of start_url
is
../start_point.html, and the manifest's URL is
https://example.com/resources/manifest.webmanifest,
then the result of parsing would be
https://example.com/start_point.html.
start_url
tracking
It's conceivable that the start_url
could be crafted to
indicate that the application was launched from outside the browser
(e.g., "start_url": "index.html?launcher=homescreen"
).
This can be useful for analytics and possibly other customizations.
However, it is also conceivable that developers could encode
strings into the start_url that uniquely identify the user (e.g., a
server assigned UUID). This is fingerprinting/privacy
sensitive information that the user might not be aware of.
Given the above, it is RECOMMENDED that, upon installation, or any time thereafter, a user agent allows the user to inspect and, if necessary, modify the start URL of an application.
theme_color
member
The theme_color
member serves as the default theme
color for an application context. What constitutes a theme
color is defined in [HTML].
If the user agent honors the value of the theme_color
member as the default theme color, then that color serves as
the theme color for all browsing contexts to which the
manifest is applied. However, a document may override the
default theme color through the inclusion of a valid [HTML]
meta
element whose name
attribute is
"theme-color".
The user agent MAY ignore the theme color's alpha component based on the context. For example, in most environments, the theme color cannot be transparent.
Implementors MAY override the value defined by the theme_color
member to support prefers-color-scheme.
background_color
member
The background_color
member describes the expected
background color of the web application. It repeats what is already
available in the application stylesheet but can be used by the
user agent to draw the background color of a web application
for which the manifest is known before the files are actually
available, whether they are fetched from the network or retrieved
from disk.
The background_color
member is only meant to improve the user
experience while a web application is loading and MUST NOT be used by
the user agent as the background color when the web
application's stylesheet is available.
Implementors MAY override the value defined by the
member to support
prefers-color-scheme.
background_color
shortcuts
member
The shortcuts
member is an array of
ShortcutItem
s that provide access to key tasks within a web
application.
Shortcuts could, for instance, be used to link directly to a user's timeline within a social media application or to their recent orders in an e-commerce context.
How shortcuts are presented, and how many of them are shown to the user, is at the discretion of the user agent and/or operating system.
Developers are encouraged to order their shortcuts by priority, with the most critical shortcuts appearing first in the array.
The steps for processing the shortcuts
member
are given by the following algorithm. The algorithm takes a
URL manifest URL, and a manifest.
ShortcutItem
shortcut of
shortcuts:
ManifestImageResource
members given
shortcut["icons"] and manifest URL.
A user agent SHOULD expose shortcuts via interactions that are consistent with exposure of an application icon's context menu in the host operating system (e.g., right click, long press). A user agent SHOULD render the shortcuts in the same order as they are provided in the manifest. A user agent SHOULD represent the shortcuts in a manner consistent with exposure of an application icon's context menu in the host operating system. A user agent MAY truncate the list of shortcuts presented in order to remain consistent with the conventions or limitations of the host operating system.
In the following example, the developer has included two shortcuts. Assuming the the manifest's URL is https://example.com/manifest.webmanifest:
{
"shortcuts": [
{
"name": "Play Later",
"description": "View the list of podcasts you saved for later",
"url": "/play-later",
"icons": [
{
"src": "/icons/play-later.svg",
"type": "image/svg+xml",
"purpose": "any"
}
]
},
{
"name": "Subscriptions",
"description": "View the list of podcasts you listen to",
"url": "/subscriptions?sort=desc"
}
]
}
ManifestImageResource
and its members
WebIDLdictionaryManifestImageResource
: ImageResource { USVStringpurpose
; };
Each
is an image that is conceptually part of
a web application, suitable to use in various contexts depending on the
semantics of the member that is using the object (e.g., an icon that is
part of an application menu, etc.).
ManifestImageResource
User agents MAY modify the images associated with an
to better match the platform’s visual style
before displaying it to the user, for example by rounding the corners
or painting it in a specific color. It is recommended that developers
prepare their image resources for such scenarios to avoid losing
important information through, e.g., change of color or clipped
corners.
ManifestImageResource
The security policy that governs whether a user agent can
fetch an icon image is governed by the img-src
directive
[CSP3] associated with the manifest's owner Document
.
For example, given the following img-src
directive in
the Content-Security-Policy
HTTP header of the
manifest's owner Document
:
HTTP/1.1 200 OK
Content-Type: text/html
Content-Security-Policy: img-src icons.example.com
<!doctype>
<html>
<link rel="manifest" href="manifest.webmanifest">
And given the following manifest.webmanifest
:
{
"name": "custom manifest",
"start_url": "https://boo",
"icons": [
{
"src": "//icons.example.com/lowres"
},
{
"src": "//other.com/hi-res"
}
]
}
The fetching of icon resources from
icons.example.com/lowres
would succeed, while fetching
from other.com/hi-res
would fail.
purpose
member
The
member is an unordered set
of unique space-separated tokens that are ASCII
case-insensitive. The allowed values are the icon
purposes.
purpose
When a
is used as an icon, a
developer can hint that the image is intended to serve some special
purpose in the context of the host OS (i.e., for better integration).
User agents SHOULD NOT use an icon other than for its stated icon
purpose.
ManifestImageResource
For example, an icon with purpose "monochrome" could be used
as a badge or pinned icon with a solid fill, visually distinct from
an application's full color launch icon. The user agent uses the
value of the
member as a hint to
determine where and how an purpose
is
displayed. Unless declared otherwise by the developer, a user agent
can use an icon for any purpose.
purpose
The icon purposes are as follows:
If an icon contains multiple purposes, it could be used for any of
those purposes. If none of the stated purposes are recognized, the
icon is totally ignored. For example, if an icon has purpose
"monochrome fizzbuzz"
, then it could be used as a
monochrome icon, as "monochrome"
is a valid purpose.
However, if an icon just has the purpose "fizzbuzz"
,
then it will be ignored.
The steps for processing the purpose
member of an image
are given by the following algorithm. The algorithm takes a
image. This
algorithm returns a set or failure.
ManifestImageResource
Some platforms have their own preferred icon shape, but as web applications should work across multiple platforms, it is possible to indicate that an icon can have a user-agent-specified mask applied by adding the maskable purpose. This allows the platform to ensure that the icon looks well integrated with the platform, and even apply different masks and background colors in different places throughout the platform.
The safe zone is the area within a maskable icon which is guaranteed to always be visible, regardless of user agent preferences. It is defined as a circle with center point in the center of the icon and with a radius of 2/5 (40%) of the icon size, which means the smaller of the icon width and height, in case the icon is not square.
Designers of maskable icons will want to make sure that all important parts are within the safe zone.
All pixels in this zone are guaranteed to be seen in all masks. Pixels outside the safe zone are not guaranteed to (but can) be visible depending on the applied mask.
The user agent MAY apply a mask of any size, making any pixels that are more than 2/5ths of the image size (minimum of width and height if non-square) away from the center (the safe zone) transparent.
The user agent MUST NOT make any pixel within the safe zone transparent.
The user agent MAY enlarge the icon by adding additional padding.
If the icon contains transparent pixels, the user agent MUST composite the icon onto a solid fill (e.g., white) of the user agent's choice.
It is suggested that designers avoid using transparent pixels in maskable icons.
By staying inside the safe zone, most icons will have around 10% padding on the top, bottom, right and left with no content or non-essential content, such as an icon background. It is suggested that developers check their icon when all but the safe zone is masked out.
As the badge purpose "monochrome" is only supported by Firefox, it is at risk of being removed from the specification. Implementers should express interest in supporting this feature if they would like it to remain in the specification.
Some platforms enforce that icons be displayed with a solid fill such as a single color, where only the transparency of the icon can be declared in a manifest. As web applications need to work across multiple platforms, it is possible to indicate that an icon can have an user-agent-specified color applied by adding the monochrome purpose. This allows the platform to ensure that the icon looks well integrated with the platform, and even apply different colors and padding in different places throughout the platform.
When processing a monochrome icon, the user agent MUST NOT independently display the red component, green component, or blue component of a pixel. The user agent SHOULD display each pixel with its original alpha value, but with a red, green, and blue value of the user agent's choosing. It is RECOMMENDED that the user agent use the same color value for all pixels.
Designers of monochrome icons could set all pixels to black and only use transparency to create a silhouette of their icon.
The user agent MAY enlarge the icon by adding additional padding.
The user agent MAY add a background of any color behind transparent pixels, and SHOULD ensure that the background has sufficient contrast with the icon.
The steps for processing ManifestImageResource
members
are given by the following algorithm. The algorithm takes an a list
of entries and a URL
manifestURL. This algorithm returns an a list of
s.
ManifestImageResource
purpose
member of an image given entry.
purpose
to purpose.
ShortcutItem
and its members
WebIDLdictionaryShortcutItem
{ required USVStringname
; USVStringshort_name
; USVStringdescription
; required USVStringurl
; sequence<ManifestImageResource
>icons
; };
Each ShortcutItem
represents a link to a key task or page within
a web app. A user agent can use these values to assemble a context menu
to be displayed by the operating system when a user engages with the
web app's icon. When the user invokes a shortcut from the operating
system menu, the user agent SHOULD run Launching a shortcut.
name
member
The name
member of a ShortcutItem
is a
string that represents the name of the shortcut as it is
usually displayed to the user in a context menu.
short_name
member
The short_name
member of a ShortcutItem
is a
string that represents a short version of the name of the
shortcut. It is intended to be used where there is insufficient space
to display the full name of the shortcut.
description
member
The description
member of a ShortcutItem
is a
string that allows the developer to describe the purpose of
the shortcut. User agents MAY expose this information to assistive
technology.
url
member
The url
member of a ShortcutItem
is a URL
within scope of a processed manifest that opens when
the associated shortcut is activated.
It's conceivable that any
could be crafted to
indicate that the application was launched from outside the browser
(e.g., url
"url": "/task/?from=homescreen"
). It is also conceivable
that developers could encode strings into the
that uniquely identify the user (e.g., a server assigned
UUID). This is fingerprinting/privacy sensitive
information that the user might not be aware of.
url
icons
member
The icons
member of an ShortcutItem
member serve as
iconic representations of the shortcut in various contexts.
When ShortcutItem
shortcut having
WebAppManifest
manifest is invoked, run the
following steps:
ExternalApplicationResource
and its members
WebIDLdictionaryExternalApplicationResource
{ required USVStringplatform
; USVStringurl
; DOMStringid
; USVStringmin_version
; sequence<Fingerprint
>fingerprints
; };
Each ExternalApplicationResource
s represents an application
related to the web application.
A valid ExternalApplicationResource
dictionary MUST have
platform
and either an url
or an
id
(or both).
platform
member
The platform the
is associated to. A
platform represents a software
distribution ecosystem or possibly an operating system. This
specification does not define the particular values for the
platform member. However, the working group maintains a
list of
known platform values in our wiki.
ExternalApplicationResource
url
member
The url
member of an ExternalApplicationResource
dictionary represents the URL at which the application can be
found.
The steps for processing the url member of an
application are given by the following algorithm. The algorithm
takes a USVString application URL. This algorithm
will return an URL or undefined
.
undefined
, return
undefined
.
undefined
.
id
member
The id
member of an ExternalApplicationResource
dictionary represents the id which is used to represent the
application on the platform.
min_version
member
The min_version
member of an
ExternalApplicationResource
dictionary represents the minimum
version of the application that is considered related to this web
app. This version is a string with platform-specific syntax
and semantics.
fingerprints
member
WebIDLdictionaryFingerprint
{ USVStringtype
; USVStringvalue
; };
The fingerprints
member of an
ExternalApplicationResource
dictionary represents an array of
Fingerprint
s.
Each Fingerprint
s represents a set of cryptographic
fingerprints used for verifying the application. A fingerprint has
the following two properties: type
and value
.
Each of these are strings, but their syntax and semantics are
platform-defined.
The following registrations are for community review and will be submitted to the IESG for review, approval, and registration with IANA.
This section contains the required text for MIME media type registration with IANA.
The application manifest MIME type is
application/manifest+json
.
If the protocol over which the manifest is transferred supports the [MIME-TYPES] specification (e.g. HTTP), it is RECOMMENDED that the manifest be labeled with the application manifest MIME type.
This specification does not directly deal with high-value data. However, installed web applications and their data could be seen as "high value" (particularly from a privacy perspective).
As the manifest format is JSON and will commonly be encoded using [UNICODE], the security considerations described in [ECMA-404] and [UNICODE-SECURITY] apply. In addition, because there is no way to prevent developers from including custom/unrestrained data in a manifest, implementors need to impose their own implementation-specific limits on the values of otherwise unconstrained member types, e.g. to prevent denial of service attacks, to guard against running out of memory, or to work around platform-specific limitations.
Web applications will generally contain ECMAScript, HTML, CSS files, and other media, which are executed in a sand-boxed environment. As such, implementors need to be aware of the security implications for the types they support. Specifically, implementors need to consider the security implications outlined in at least the following specifications: [CSS-MIME], [ECMAScript-MIME], [HTML].
As web applications can contain content that is able to simultaneously interact with the local device and a remote host, implementors need to consider the privacy implications resulting from exposing private information to a remote host. Mitigation and in-depth defensive measures are an implementation responsibility and not prescribed by this specification. However, in designing these measures, implementors are advised to enable user awareness of information sharing, and to provide easy access to interfaces that enable revocation of permissions.
As this specification allows for the declaration of URLs within certain members of a manifest, implementors need to consider the security considerations discussed in the [URL] specification. Implementations intending to display IRIs and IDNA addresses found in the manifest are strongly encouraged to follow the security advice given in [UNICODE-SECURITY].
Developers need to be aware of the security considerations
discussed throughout the [CSP3] specification, particularly in
relation to making data:
a valid source for the
purpose of inlining
a manifest. Doing so can enable XSS
attacks by allowing a manifest to be included directly in the
document itself; this is best avoided completely.
A request to register the manifest
link relation type
been submitted to IANA.
This document reuses text from the [HTML] specification, as permitted by the license of that specification.
Dave Raggett and Dominique Hazael-Massieux contributed to this specification via the HTML5Apps project.
Claudio Gomboli for icon example images.
Indiana University Bloomington security researchers have contributed to this specification by reporting potential risks related to out-of-scope navigation.
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, MUST NOT, OPTIONAL, RECOMMENDED, SHOULD, and SHOULD NOT in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
There is only one class of product that can claim conformance to this specification: a user agent.
Although this specification is primarily targeted at web browsers, it is feasible that other software could also implement this specification in a conforming manner. For instance, search engines, or crawlers, could find and process manifests to build up catalogs of sites that potentially work as installable web applications.
This section is non-normative.
This specification is designed to be extensible. Other specifications are encouraged to define new members for the manifest. However, in doing so, please follow the conventions used in this specification. In particular, use the extension point to hook into the steps for processing a manifest. Also, be sure to specify the steps for processing your particular member in the manner set forth in this specification. This will help keep this part of the platform consistent.
To allow the community to easily find extensions, please add your extensions to the Extensions Registry.
When specifying a new member, don't override or monkey patch anything defined in this specification. Also, don't assume your member will be processed before or after any other member. Keep your new member, and its processing, atomic and self contained. Note also that implementations are free to ignore any member they do not recognize or support.
If you are writing a specification and temporarily want to patch this specification to help implementations along, file a bug so the community is informed of what you are trying to do.
This section is non-normative.
Although proprietary extensions are undesirable, they can't realistically be avoided. As such, the RECOMMENDED way to add a new proprietary manifest member as an extension is to use a vendor prefix.
We encourage implementors to add proprietary extensions to our Extensions Registry. This allows the community to track what extensions vendors and/or the web community have defined and documented. Periodically, we will consider those extensions for standardization.
The following is an example of three hypothetical vendor extensions.
{
...
"webkit_fancy_feature": "some/url/img",
"moz_awesome_thing": { ... },
"vendor_example_site_verification": "KEY_9864D0966935"
...
}
Extensions to this specification are being incubated in parallel by the Web Community, some of which are shipping in multiple browsers. If two or more browser engines end up supporting an incubated feature, then those features will become part of this specification in the future - allowing them to become a standard the Web Platform:
BeforeInstallPrompt
and window.onappinstalled
event
BeforeInstallPrompt
event and window.onappinstalled
event
were originally part of this specification. However, they were
removed from the
specification because they did not have support from two or more
implementers. You can now find them in the BeforeInstallPrompt
event and window.onappinstalled
repository at the WICG.
share_target
member
share_target
member registers a web application as "target" for
share actions (e.g., for sharing a text, a URL, or a file). The
share_target
member is part of the Web Share Target
specification, being incubated at the WICG.
Several members of the Web App Manifest provide additional metadata related to how the web application may be presented in the context of a digital storefront, installation dialog, or other surfaces where this web application may be marketed or distributed. In an effort to support these use cases better, the following members have been moved into Web App Manifest - Application Information:
categories
description
iarc_rating_id
screenshots
link
and meta
elements
An extensive discussion of why we chose to use JSON instead of HTML
meta
/link
tags for this specification is
available on GitHub and on the
www-tag
list. Below is a short summary of the key points raised in those
discussions.
The document format defined in this specification provides a unified
means of encapsulating metadata about a Web application in a way that
we hope will avoid existing pitfalls with both proprietary and
[HTML]'s meta
/link
tags. Those pitfalls
include:
Although it would be unrealistic to think that this specification won't bring its own set of problems, externalizing this data in the form of a manifest solves the problems described above. These problems are solved by:
meta
tags are currently using, especially when a tag's
value contains several sub-values.
In addition, standardizing the functionality currently provided by the
various meta
tag-based solutions within the manifest
solves the problem of having to declare large number of proprietary and
standard [HTML] tags that all achieve the same thing. Of course, this
hinges on the standard actually getting implemented by browsers and
those browsers getting widely deployed to users: if this happens, the
Web community might be able to retire many of the proprietary
meta
tags plaguing the Web at the time of writing. More
information about the proprietary tags can be found in the
Use
Cases and Requirements for Installable Web Apps .
Lastly, this specification does not make the standardized solutions
found in [HTML] redundant. When members like the name
or
icons
is missing from the manifest, user agents can search
in a manifest's owner [HTML] document for things like icons and the
application name (or a user agent might even fallback to proprietary
tags/metadata, if they are present in a document).
Developers interested in validating manifest documents can find an unofficial JSON schema for the manifest format at schemastore.org. It is licensed under Apache 2.0. It is kindly maintained by Mads Kristensen. If you find any issues with the JSON schema, please file a bug at the SchemaStore repository on GitHub.
This section is non-normative.
It is expected that authors will localize the content of a manifest by using one of the following options:
Accept-Language
" header, or even a custom HTTP header).
Given the options above, developers need to be mindful of the end-user's privacy with respect to their preferred language: When the end-user has explicitly indicated their language preference to a web application (i.e., when not just using the user-agent default language settings), sending the end-user's preferred language in the clear over the wire is generally not OK. Doing so would reveal personal information about an end-user. As such, developers are encouraged to use [TLS] to reduce the chances of pervasive monitoring of their Web applications [RFC7258].
This document attempts to address the Use Cases and Requirements for Installable Web Apps.
WebIDLdictionaryWebAppManifest
{TextDirectionType
dir
= "auto"; DOMStringlang
; USVStringname
; USVStringshort_name
; sequence<ManifestImageResource
>icons
; USVStringstart_url
;DisplayModeType
display
= "browser"; OrientationLockTypeorientation
; USVStringtheme_color
; USVStringbackground_color
; USVStringscope
; sequence<ExternalApplicationResource
>related_applications
; booleanprefer_related_applications
= "false"; sequence<ShortcutItem
>shortcuts
; }; enumTextDirectionType
{ "ltr
", "rtl
", "auto
" }; enumDisplayModeType
{ "fullscreen
", "standalone
", "minimal-ui
", "browser
" }; dictionaryManifestImageResource
: ImageResource { USVStringpurpose
; }; dictionaryShortcutItem
{ required USVStringname
; USVStringshort_name
; USVStringdescription
; required USVStringurl
; sequence<ManifestImageResource
>icons
; }; dictionaryExternalApplicationResource
{ required USVStringplatform
; USVStringurl
; DOMStringid
; USVStringmin_version
; sequence<Fingerprint
>fingerprints
; }; dictionaryFingerprint
{ USVStringtype
; USVStringvalue
; };
As the manifest uses the JSON format, this specification relies on the
types defined in [ECMA-404] specification: namely object,
array, number, string,
true
, false
, and undefined
.
Strict type checking is not enforced by this specification. Instead,
each member's definition specifies the steps required to process a
particular member and what to do when a type does not match what is
expected.
This section is non-normative.
The following are normative changes since last publication.
"auto"
enum value for TextDirectionType
§7.1background_color
member for WebAppManifest
§7.13"browser"
enum value for DisplayModeType
§4.description
member for ShortcutItem
§9.3dir
member for WebAppManifest
§7.1display
member for WebAppManifest
§7.7display-mode
§4.2DisplayModeType
enum
§4.ExternalApplicationResource
dictionary
§10.Fingerprint
dictionary
§10.5fingerprints
member for ExternalApplicationResource
§10.5"fullscreen"
enum value for DisplayModeType
§4.id
member for ExternalApplicationResource
§10.3lang
member for WebAppManifest
§7.2"ltr"
enum value for TextDirectionType
§7.1ManifestImageResource
dictionary
§8.min_version
member for ExternalApplicationResource
§10.4"minimal-ui"
enum value for DisplayModeType
§4.orientation
member for WebAppManifest
§7.8prefer_related_applications
member for WebAppManifest
§7.12purpose
member for ManifestImageResource
§8.2related_applications
member for WebAppManifest
§7.11"rtl"
enum value for TextDirectionType
§7.1scope
member for WebAppManifest
§7.5ShortcutItem
dictionary
§9.shortcuts
member for WebAppManifest
§7.14"standalone"
enum value for DisplayModeType
§4.start_url
member for WebAppManifest
§7.9TextDirectionType
enum
§7.1theme_color
member for WebAppManifest
§7.10type
member for Fingerprint
§10.5value
member for Fingerprint
§10.5WebAppManifest
dictionary
§7.CSS
)
Document
interface
Document
)
response
)
link
element
meta
element
ImageResource
list
)
set
)
string
)
list
)
iteration
)
list
)
list
)
@media
)
OrientationLockType
enum
url
)
boolean
type
DOMString
interface
USVString
interface