1. Introduction
This section is non-normative.
This is a proposal to bring an asynchronous cookie API to scripts running in HTML documents and service workers.
HTTP cookies have, since their origins at Netscape (documentation preserved by archive.org), provided a valuable state-management mechanism for the web.
The synchronous single-threaded script-level document.cookie
interface to cookies has been a source of complexity and performance woes further exacerbated by the move in many browsers from:
-
a single browser process,
-
a single-threaded event loop model, and
-
no general expectation of responsiveness for scripted event handling while processing cookie operations
... to the modern web which strives for smoothly responsive high performance:
-
in multiple browser processes,
-
with a multithreaded, multiple-event loop model, and
-
with an expectation of responsiveness on human-reflex time scales.
On the modern web a cookie operation in one part of a web application cannot block:
-
the rest of the web application,
-
the rest of the web origin, or
-
the browser as a whole.
Newer parts of the web built in service workers need access to cookies too but cannot use the synchronous, blocking document.cookie
interface at all as they both have no document
and also cannot block the event loop as that would interfere with handling of unrelated events.
1.1. A Taste of the Proposed Change
Although it is tempting to rethink cookies entirely, web sites today continue to rely heavily on them, and the script APIs for using them are largely unchanged over their first decades of usage.
Today writing a cookie means blocking your event loop while waiting for the browser to synchronously update the cookie jar with a carefully-crafted cookie string in Set-Cookie
format:
document. cookie= '__Secure-COOKIENAME=cookie-value' + '; Path=/' + '; expires=Fri, 12 Aug 2016 23:05:17 GMT' + '; Secure' + '; Domain=example.org' ; // now we could assume the write succeeded, but since // failure is silent it is difficult to tell, so we // read to see whether the write succeeded var successRegExp= /(^|; ?)__Secure-COOKIENAME=cookie-value(;|$)/ ; if ( String( document. cookie). match( successRegExp)) { console. log( 'It worked!' ); } else { console. error( 'It did not work, and we do not know why' ); }
What if you could instead write:
cookieStore. set( '__Secure-COOKIENAME' , 'cookie-value' , { expires: Date. now() + 24 * 60 * 60 * 1000 , domain: 'example.org' }). then( function () { console. log( 'It worked!' ); }, function ( reason) { console. error( 'It did not work, and this is why:' , reason); }); // Meanwhile we can do other things while waiting for // the cookie store to process the write...
This also has the advantage of not relying on document
and not blocking, which together make it usable from Service Workers, which otherwise do not have cookie access from script.
This proposal also includes a power-efficient monitoring API to replace setTimeout
-based polling cookie monitors with cookie change observers.
1.2. Summary
This proposal outlines an asynchronous API using Promises/async functions for the following cookie operations:
-
write (or "set") and delete (or "expire") cookies
-
read (or "get") script-visible cookies
-
... including for specified in-scope request paths in service worker contexts
-
-
monitor script-visible cookies for changes using
CookieChangeEvent
-
... in long-running script contexts (e.g.
document
) -
... after registration during the
InstallEvent
in ephemeral service worker contexts -
... again including for script-supplied in-scope request paths in service worker contexts
-
1.2.1. Script visibility
A cookie is script-visible when it is in-scope and does not have the HttpOnly
cookie flag.
1.2.2. Motivations
Some service workers need access to cookies but
cannot use the synchronous, blocking document.cookie
interface as they both have no document
and
also cannot block the event loop as that would interfere with handling of unrelated events.
A new API may also provide a rare and valuable chance to address some outstanding cross-browser incompatibilities and bring divergent specs and user-agent behavior into closer correspondence.
A well-designed and opinionated API may actually make cookies easier to deal with correctly from scripts, with the potential effect of reducing their accidental misuse. An efficient monitoring API, in particular, can be used to replace power-hungry polling cookie scanners.
The API must interoperate well enough with existing cookie APIs (HTTP-level, HTML-level and script-level) that it can be adopted incrementally by a large or complex website.
1.2.3. Opinions
This API defaults cookie paths to /
for cookie write operations, including deletion/expiration. The implicit relative path-scoping of cookies to .
has caused a lot of additional complexity for relatively little gain given their security equivalence under the same-origin policy and the difficulties arising from multiple same-named cookies at overlapping paths on the same domain. Cookie paths without a trailing /
are treated as if they had a trailing /
appended for cookie write operations. Cookie paths must start with /
for write operations, and must not contain any ..
path segments. Query parameters and URL fragments are not allowed in paths for cookie write operations.
URLs without a trailing /
are treated as if the final path segment had been removed for cookie read operations, including change monitoring. Paths for cookie read operations are resolved relative to the default read cookie path.
This API defaults cookies to "Secure" when they are written from a secure web origin. This is intended to prevent unintentional leakage to unsecured connections on the same domain. Furthermore it disallows (to the extent permitted by the browser implementation) creation or modification of Secure-
flagged cookies from unsecured web origins and enforces special rules for the __Host- and __Secure- cookie name prefixes.
This API defaults cookies to "Domain"-less, which in conjunction with "Secure" provides origin-scoped cookie
behavior in most modern browsers. When practical the __Host-
cookie name prefix should be used with these cookies so that cooperating browsers origin-scope them.
Serialization of expiration times for non-session cookies in a special cookie-specific format has proven cumbersome, so this API allows JavaScript Date objects and numeric timestamps (milliseconds since the beginning of the Unix epoch) to be used instead. The inconsistently-implemented Max-Age parameter is not exposed, although similar functionality is available for the specific case of expiring a cookie.
Cookies without U+003D (=) code points in their HTTP Cookie header serialization are treated as having an empty name, consistent with the majority of current browsers. Cookies with an empty name cannot be set using values containing U+003D (=) code points as this would result in ambiguous serializations in the majority of current browsers.
Internationalized cookie usage from scripts has to date been slow and browser-specific due to lack of interoperability because although several major browsers use UTF-8 interpretation for cookie data, historically Safari and browsers based on WinINet have not. This API mandates UTF-8 interpretation for cookies read or written by this API.
Use of cookie-change-driven scripts has been hampered by the absence of a power-efficient (non-polling) API for this. This API provides observers for efficient monitoring in document contexts and interest registration for efficient monitoring in service worker contexts.
Scripts should not have to write and then read "test cookies" to determine whether script-initiated cookie write access is possible, nor should they have to correlate with cooperating server-side versions of the same write-then-read test to determine that script-initiated cookie read access is impossible despite cookies working at the HTTP level.
1.2.4. Compatiblity
Some user-agents implement non-standard extensions to cookie behavior. The intent of this specification,
though, is to first capture a useful and interoperable (or mostly-interoperable) subset of cookie behavior implemented
across modern browsers. As new cookie features are specified and adopted it is expected that this API will be
extended to include them. A secondary goal is to converge with document.cookie
behavior
and the http cookie specification. See https://github.com/whatwg/html/issues/804 and https://inikulin.github.io/cookie-compat/
for the current state of this convergence.
Differences across browsers in how bytes outside the printable-ASCII subset are interpreted has led to
long-lasting user- and developer-visible incompatibilities across browsers making internationalized use of cookies
needlessly cumbersome. This API requires UTF-8 interpretation of cookie data and uses USVString
for the script interface,
with the additional side-effects that subsequent uses of document.cookie
to read a cookie read or written through this interface and subsequent uses of document.cookie
to update a cookie previously read or written through this interface will also use a UTF-8 interpretation of the cookie data. In practice this
will change the behavior of WinINet
-based user agents and Safari but should bring their behavior into concordance
with other modern user agents.
1.3. Querying Cookies
Both documents and service workers access the same query API, via the cookieStore
property on the global object.
The get()
and getAll()
methods on CookieStore
are used to query cookies.
Both methods return promises.
Both methods take the same arguments, which can be either:
-
a name, or
-
a optional dictionary of options
The get()
method is essentially a form of getAll()
that only returns the first result.
try { const cookie= await cookieStore. get( 'session_id' ); if ( cookie) { console. log( `Found ${ cookie. name} cookie: ${ cookie. value} ` ); } else { console. log( 'Cookie not found' ); } } catch ( e) { console. error( `Cookie store error: ${ e} ` ); }
try { const cookies= await cookieStore. getAll({ name: 'session_' , matchType: 'starts-with' , }); for ( const cookieof cookies) console. log( `Result: ${ cookie. name} = ${ cookie. value} ` ); } catch ( e) { console. error( `Cookie store error: ${ e} ` ); }
Service workers can obtain the list of cookies that would be sent by a fetch to any URL under their scope.
await cookieStore. getAll({ url: '/admin' });
Documents can only obtain the cookies at their current URL. In other words,
the only valid url
value in Document contexts is the document’s URL.
The objects returned by get()
and getAll()
contain all the relevant information in the cookie store, not just the name and the value as in the older document.cookie
API.
await cookie= cookieStore. get( 'session_id' ); console. log( `Cookie scope - Domain: ${ cookie. domain} Path: ${ cookie. path} ` ); if ( cookie. expires=== null ) { console. log( 'Cookie expires at the end of the session' ); } else { console. log( `Cookie expires at: ${ cookie. expires} ` ); } if ( cookie. secure) console. log( 'The cookie is restricted to secure origins' );
1.4. Modifying Cookies
Both documents and service workers access the same modification API, via the cookieStore
property on the global object.
Cookies are created or modified (written) using the set()
method.
try { await cookieStore. set( 'opted_out' , '1' ); } catch ( e) { console. error( `Failed to set cookie: ${ e} ` ); }
The set()
call above is a shorthand for the following:
await cookieStore. set({ name: 'opted_out' , value: '1' , expires: null , // session cookie // By default, cookies are scoped at the current domain. domain: ( new URL( self. location. href)). hostname, path: '/' , // Creates secure cookies by default on secure origins. secure: true , });
Cookies are deleted (expired) using the delete()
method.
try { await cookieStore. delete ( 'session_id' ); } catch ( e) { console. error( `Failed to delete cookie: ${ e} ` ); }
Under the hood, deleting a cookie is done by changing the cookie’s expiration date to the past, which still works.
try { const one_day_ms= 24 * 60 * 60 * 1000 ; await cookieStore. set( 'session_id' , 'value will be ignored' , { expires: Date. now() - one_day_ms}); } catch ( e) { console. error( `Failed to delete cookie: ${ e} ` ); }
1.5. Monitoring Cookies
To avoid polling, it is possible to observe changes to cookies.
In documents, change
events are fired for all relevant cookie changes.
change
events in documents:
cookieStore. addEventListener( 'change' , event=> { console. log( ` ${ event. changed. length} changed cookies` ); for ( const cookiein event. changed) console. log( `Cookie ${ cookie. name} changed to ${ cookie. value} ` ); console. log( ` ${ event. deleted. length} deleted cookies` ); for ( const cookiein event. deleted) console. log( `Cookie ${ cookie. name} deleted` ); });
Service workers have to subscribe for events during the install stage,
and start receiving cookiechange
events when activated.
cookiechange
events in a service worker:
self. addEventListener( 'install' , event=> { event. waitFor( async() => { await cookieStore. subscribeToChanges([{ name: 'session' , // Get change events for session-related cookies. matchType: 'starts-with' , // Matches session_id, session-id, etc. }]); }); }); self. addEventListener( 'cookiechange' , event=> { // The event has |changed| and |deleted| properties with // the same semantics as the Document events. console. log( ` ${ event. changed. length} changed cookies` ); console. log( ` ${ event. deleted. length} deleted cookies` ); });
Calls to subscribeToChanges()
are cumulative, so that independently maintained
modules or libraries can set up their own subscriptions. As expected, a service worker's
subscriptions are persisted for with the service worker registration.
Subscriptions can use the same options as get()
and getAll()
.
The complexity of fine-grained subscriptions is justified
by the cost of dispatching an irrelevant cookie change event to a service worker,
which is is much higher than the cost of dispatching an equivalent event
to a window. Specifically, dispatching an event to a service worker might
require waking up the worker, which has a significant impact on battery life.
The getChangeSubscriptions()
allows a service worker to introspect
the subscriptions that have been made.
const subscriptions= await cookieStore. getChangeSubscriptions(); for ( const subof subscriptions) { console. log( sub. name, sub. url, sub. matchType); }
2. Concepts
2.1. Cookie
A cookie is normatively defined for user agents by Cookies: HTTP State Management Mechanism §User Agent Requirements.
2.2. Cookie Store
A cookie store is normatively defined for user agents by Cookies: HTTP State Management Mechanism §User Agent Requirements.
When any of the following conditions occur for a cookie store, perform the steps to process cookie changes.
-
A newly-created cookie is inserted into the cookie store.
-
A user agent evicts expired cookies from the cookie store.
-
A user agent removes excess cookies from the cookie store.
How about when "the current session is over" for non-persistent cookies?
2.3. Extensions to Service Worker
[Service-Workers] defines service worker registration, which this specification extends.
A service worker registration has an associated cookie change subscription list which is a list; each member is a cookie change subscription. A cookie change subscription is a tuple of name, url, and matchType.
3. The CookieStore
Interface
[Exposed =(ServiceWorker ,Window ),SecureContext ]interface :
CookieStore EventTarget {Promise <CookieListItem ?>get (USVString );
name Promise <CookieListItem ?>get (optional CookieStoreGetOptions = {});
options Promise <CookieList >getAll (USVString );
name Promise <CookieList >getAll (optional CookieStoreGetOptions = {});
options Promise <void >set (USVString ,
name USVString ,
value optional CookieStoreSetOptions = {});
options Promise <void >set (CookieStoreSetExtraOptions );
options Promise <void >delete (USVString );
name Promise <void >delete (CookieStoreDeleteOptions ); [
options Exposed =ServiceWorker ]Promise <void >subscribeToChanges (sequence <CookieStoreGetOptions >); [
subscriptions Exposed =ServiceWorker ]Promise <sequence <CookieStoreGetOptions >>getChangeSubscriptions (); [Exposed =Window ]attribute EventHandler ; };
onchange enum {
CookieMatchType ,
"equals" };
"starts-with" dictionary {
CookieStoreGetOptions USVString ;
name USVString ;
url CookieMatchType = "equals"; };
matchType enum {
CookieSameSite ,
"strict" ,
"lax" };
"none" dictionary {
CookieStoreSetOptions DOMTimeStamp ?=
expires null ;USVString ?=
domain null ;USVString = "/";
path boolean =
secure true ;CookieSameSite = "strict"; };
sameSite dictionary :
CookieStoreSetExtraOptions CookieStoreSetOptions {required USVString ;
name required USVString ; };
value dictionary {
CookieStoreDeleteOptions required USVString ;
name USVString ?=
domain null ;USVString = "/"; };
path dictionary {
CookieListItem required USVString ;
name USVString ;
value USVString ?=
domain null ;USVString = "/";
path DOMTimeStamp ?=
expires null ;boolean =
secure true ;CookieSameSite = "strict"; };
sameSite typedef sequence <CookieListItem >;
CookieList
3.1. The get()
method
- cookie = await cookieStore .
get
(name)- cookie = await cookieStore .
get
(options) - cookie = await cookieStore .
- Returns a promise resolving to the first in-scope script-visible value
for a given cookie name (or other options).
In a service worker context this defaults to the path of the service worker’s registered scope.
In a document it defaults to the path of the current document and does not respect changes from
replaceState()
ordocument.domain
.
get(name)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Return p.
get(options)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
If options’
url
dictionary member is present, then run these steps:-
Let parsed be the result of parsing options’
url
dictionary member with the context object's relevant settings object's API base URL. -
If the current global object is a
Window
object and parsed does not equal url, then return a promise rejected with aTypeError
. -
If parsed’s origin and url’s origin are not the same origin, then return a promise rejected with a
TypeError
. -
Set url to parsed.
-
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Return p.
3.2. The getAll()
method
- cookies = await cookieStore .
getAll
(name)- cookies = await cookieStore .
getAll
(options) - cookies = await cookieStore .
-
Returns a promise resolving to the all in-scope script-visible value for a given cookie name (or other options). In a service worker context this defaults to the path of the service worker’s registered scope. In a document it defaults to the path of the current document and does not respect changes from
replaceState()
ordocument.domain
.
getAll(name)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Let list be the results of running query cookies with url and name.
-
Otherwise, resolve p with list.
-
-
Return p.
getAll(options)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
If options’
url
dictionary member is present, then run these steps:-
Let parsed be the result of parsing options’
url
dictionary member with the context object's relevant settings object's API base URL. -
If the current global object is a
Window
object and parsed does not equal url, then return a promise rejected with aTypeError
. -
If parsed’s origin and url’s origin are not the same origin, then return a promise rejected with a
TypeError
. -
Set url to parsed.
-
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Return p.
3.3. The set()
method
- await cookieStore .
set
(name, value)- await cookieStore .
set
(options) - await cookieStore .
-
Writes (creates or modifies) a cookie.
The options default to:
-
Path:
/
-
Domain: same as the domain of the current document or service worker’s location
-
No expiry date
-
Secure flag: set (cookie only transmitted over secure protocol)
-
SameSite: strict
-
set(name, value, options)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Let r be the result of running set a cookie with url, name, value, options’
expires
dictionary member, options’domain
dictionary member, options’path
dictionary member, options’secure
dictionary member, and options’sameSite
dictionary member. -
If r is failure, then reject p with a
TypeError
and abort these steps. -
Resolve p with undefined.
-
-
Return p.
set(options)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Let r be the result of running set a cookie with url, options’
name
dictionary member, options’value
dictionary member, options’expires
dictionary member, options’domain
dictionary member, options’path
dictionary member, options’secure
dictionary member, and options’sameSite
dictionary member. -
If r is failure, then reject p with a
TypeError
and abort these steps. -
Resolve p with undefined.
-
-
Return p.
3.4. The delete()
method
delete(name)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Let r be the result of running delete a cookie with url, name, null, "
/
", true, and "strict
". -
If r is failure, then reject p with a
TypeError
and abort these steps. -
Resolve p with undefined.
-
-
Return p.
delete(options)
method, when invoked, must run these steps:
-
Let origin be the current settings object's origin.
-
If origin is an opaque origin, then return a promise rejected with a "
SecurityError
"DOMException
. -
Let url be the current settings object's creation URL.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Return p.
3.5. The subscribeToChanges()
method
- await cookieStore .
subscribeToChanges
(subscriptions) -
This method can only be called during a Service Worker install phase.
Once subscribed, notifications are delivered as "
cookiechange
" events fired against the Service Worker's global scope:
subscribeToChanges(subscriptions)
method, when invoked, must run these steps:
-
Let serviceWorker be the context object's global object's service worker.
-
If serviceWorker’s state is not installing, then return a promise rejected with a
TypeError
. -
Let registration be serviceWorker’s associated containing service worker registration.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
For each entry in subscriptions, run these steps:
-
Let name be entry’s
name
member. -
Let url be the result of parsing entry’s
url
dictionary member with the context object's relevant settings object's API base URL. -
If url does not start with registration’s scope url, then reject p with a
TypeError
and abort these steps. -
Let matchType be entry’s
matchType
member. -
Let subscription be the cookie change subscription (name, url, matchType).
-
Append subscription to registration’s associated cookie change subscription list.
-
-
Resolve p with undefined.
-
-
Return p.
3.6. The getChangeSubscriptions()
method
- subscriptions = await cookieStore .
getChangeSubscriptions()
- This method returns a promise which resolves to a list of the cookie change subscriptions made for this Service Worker registration.
getChangeSubscriptions()
method, when invoked, must run these steps:
-
Let serviceWorker be the context object's global object's service worker.
-
Let registration be serviceWorker’s associated containing service worker registration.
-
Let p be a new promise.
-
Run the following steps in parallel:
-
Let subscriptions be registration’s associated cookie change subscription list.
-
Let result be a new list.
-
For each subscription in subscriptions, run these steps:
-
Resolve p with result.
-
-
Return p.
4. Event Interfaces
4.1. The CookieChangeEvent
interface
A CookieChangeEvent
is dispatched against CookieStore
objects
in Window
contexts when any script-visible cookie changes have occurred.
[Exposed =Window ,SecureContext ]interface :
CookieChangeEvent Event {(
constructor DOMString ,
type optional CookieChangeEventInit = {});
eventInitDict readonly attribute CookieList ;
changed readonly attribute CookieList ; };
deleted dictionary :
CookieChangeEventInit EventInit {CookieList ;
changed CookieList ; };
deleted
The changed
and deleted
attributes must return the value they were initialized to.
4.2. The ExtendableCookieChangeEvent
interface
An ExtendableCookieChangeEvent
is dispatched against ServiceWorkerGlobalScope
objects when any script-visible cookie changes have occurred which match the Service Worker's cookie change subscription list.
[Exposed =ServiceWorker ]interface :
ExtendableCookieChangeEvent ExtendableEvent {(
constructor DOMString ,
type optional ExtendableCookieChangeEventInit = {});
eventInitDict readonly attribute CookieList ;
changed readonly attribute CookieList ; };
deleted dictionary :
ExtendableCookieChangeEventInit ExtendableEventInit {CookieList ;
changed CookieList ; };
deleted
The changed
and deleted
attributes must return the value they were initialized to.
5. Global Interfaces
A CookieStore
is accessed by script using an attribute in the global
scope in a Window
or ServiceWorkerGlobalScope
context.
5.1. The Window
interface
[SecureContext ]partial interface Window { [Replaceable ,SameObject ]readonly attribute CookieStore ; };
cookieStore
The cookieStore
attribute’s getter must return context object's relevant settings object's CookieStore
object.
5.2. The ServiceWorkerGlobalScope
interface
partial interface ServiceWorkerGlobalScope { [Replaceable ,SameObject ]readonly attribute CookieStore ;
cookieStore attribute EventHandler ; };
oncookiechange
The cookieStore
attribute’s getter must return context object's relevant settings object's CookieStore
object.
6. Algorithms
Cookie attribute-values are stored as byte sequences, not strings.
To encode a string, run UTF-8 encode on string.
To decode a value, run UTF-8 decode without BOM on value.
6.1. Query Cookies
To query cookies with url, optional name, and optional matchType, run the following steps:
-
Perform the steps defined in Cookies: HTTP State Management Mechanism §The Cookie Header to "compute the cookie-string from a cookie store" with url as request-uri. The cookie-string itself is ignored, but the intermediate cookie-list is used in subsequent steps.
For the purposes of the steps, the cookie-string is being generated for a "non-HTTP" API.
-
Let list be a new list.
-
For each cookie in cookie-list, run these steps:
-
Assert: cookie’s http-only-flag is false.
-
If name is given, then run these steps:
-
Let item be the result of running create a CookieListItem from cookie.
-
Append item to list.
-
-
Return list.
A cookieName matches matchName using matchType if the following steps return true:
-
Switch on matchType:
- unspecified
-
Return true.
- "
equals
" -
If cookieName does not equal matchName, then return false.
- "
starts-with
" -
If cookieName does not start with matchName, then return false.
-
Return true.
Note: If matchName is the empty string and matchType is "starts-with
",
then all cookieNames are matched.
To create a CookieListItem
from cookie, run the following steps.
-
Let item be a new
CookieListItem
. -
Set item’s
name
dictionary member to cookie’s name (decoded). -
Set item’s
value
dictionary member to cookie’s value (decoded). -
Set item’s
domain
dictionary member to cookie’s domain (decoded). -
Set item’s
path
dictionary member to cookie’s path (decoded). -
Set item’s
expires
dictionary member to cookie’s expiry-time (as a timestamp). -
Set item’s
secure
dictionary member to cookie’s secure-only-flag. -
Switch on cookie’s same-site-flag:
-
Return item.
Note: The cookie’s creation-time, last-access-time, persistent-flag, host-only-flag, and http-only-flag attributes are not exposed to script.
Note: This is the same representation used for time values in [ECMAScript].
6.2. Set a Cookie
To set a cookie with url, name, value, optional expires, domain, path, secure flag, and sameSite, run the following steps:
-
If name’s length is 0 and value contains U+003D (
=
), then return failure. -
Let host be url’s host
-
If domain is not null, then run these steps:
-
If domain starts with U+002D (
.
), then return failure. -
If host does not equal domain and host does not end with U+002D (
.
) followed by domain, then return failure.
-
-
Otherwise, if domain is null, then set domain to host.
-
If secure is false and name starts with either "
__Secure-
" or "__Host-
", then return failure. -
Let attributes be a list.
-
If expires is given, then append `
Expires
`/expires (date serialized) to attributes. -
If secure is true, then append `
Secure
`/`` to attributes. -
Switch on sameSite:
-
Perform the steps defined in Cookies: HTTP State Management Mechanism §Storage Model for when the user agent "receives a cookie" with url as request-uri, name (encoded) as cookie-name, value (encoded) as cookie-value, and attributes as cookie-attribute-list.
For the purposes of the steps, the newly-created cookie was received from a "non-HTTP" API.
-
Return success.
Note: Storing the cookie may still fail due to requirements in [RFC6265bis] but these steps will be considered successful.
DOMTimeStamp
millis,
let dateTime be the date and time millis milliseconds after 00:00:00 UTC, 1 January 1970
(assuming that there are exactly 86,400,000 milliseconds per day),
and return a byte sequence corresponding to the closest cookie-date
representation of dateTime according to Cookies: HTTP State Management Mechanism §Dates. 6.3. Delete a Cookie
To delete a cookie with url, name, domain and path, run the following steps:
-
Let expires be the earliest representable date represented as a timestamp.
Note: The exact value of expires is not important for the purposes of this algorithm, as long as it is in the past.
-
Let value be the empty string.
-
Let secure be true.
-
Let sameSite be "
strict
".Note: The values for value, secure, and sameSite will not be persisted by this algorithm.
-
Return the results of running set a cookie with url, name, value, expires, domain, path, secure, and sameSite.
6.4. Process Changes
To process cookie changes, run the following steps:
-
For every
Window
window, run the following steps:-
Let url be window’s creation URL.
-
Let changes be the observable changes for url.
-
Queue a task to fire a change event named "
change
" with changes at window’sCookieStore
on window’s responsible event loop.
-
-
For every service worker registration registration, run the following steps:
-
Let changes be a new set.
-
For each change in the observable changes for registration’s scope url, run these steps:
-
Let cookie be change’s cookie.
-
For each subscription in registration’s cookie change subscription list, run these steps:
-
-
Let changedList and deletedList be the result of running prepare lists using changes for registration.
-
Fire a functional event named "
cookiechange
" usingExtendableCookieChangeEvent
on registration with these properties:
-
The observable changes for url are the set of cookie changes to cookies in a cookie store which meet the requirements in step 1 of Cookies: HTTP State Management Mechanism §The Cookie Header's steps to "compute the cookie-string from a cookie store" with url as request-uri, for a "non-HTTP" API.
A cookie change is a cookie and a type (either changed or deleted):
-
A cookie which is removed due to an insertion of another cookie with the same name, domain, and path is ignored.
-
A newly-created cookie which is not immediately evicted is considered changed.
-
A newly-created cookie which is immediately evicted is considered deleted.
-
A cookie which is otherwise evicted or removed is considered deleted
To fire a change event named type with changes at target, run the following steps:
-
Let event be the result of creating an Event using
CookieChangeEvent
. -
Set event’s
type
attribute to type. -
Set event’s
bubbles
andcancelable
attributes to false. -
Let changedList and deletedList be the result of running prepare lists using changes for target.
-
Set event’s
changed
attribute to changedList. -
Set event’s
deleted
attribute to deletedList. -
Dispatch event at target.
To prepare lists using changes for target, run the following steps:
-
Let changedList be a new list.
-
Let deletedList be a new list.
-
For each change in changes, run these steps:
-
Let item be the result of running create a CookieListItem from change’s cookie.
-
If change’s type is changed, then append item to changedList.
-
Otherwise, run these steps:
-
-
Return changedList and deletedList.
7. Security
Other than cookie access from service worker contexts, this API is not intended to expose any new capabilities to the web.
7.1. Gotcha!
Although browser cookie implementations are now evolving in the direction of better security and fewer surprising and error-prone defaults, there are at present few guarantees about cookie data security.
-
unsecured origins can typically overwrite cookies used on secure origins
-
superdomains can typically overwrite cookies seen by subdomains
-
cross-site scripting attacts and other script and header injection attacks can be used to forge cookies too
-
cookie read operations (both from script and on web servers) don’t give any indication of where the cookie came from
-
browsers sometimes truncate, transform or evict cookie data in surprising and counterintuitive ways
-
... due to reaching storage limits
-
... due to character encoding differences
-
... due to differing syntactic and semantic rules for cookies
-
For these reasons it is best to use caution when interpreting any cookie’s value, and never execute a cookie’s value as script, HTML, CSS, XML, PDF, or any other executable format.
7.2. Restrict?
This API may have the unintended side-effect of making cookies easier to use and consequently encouraging their further use. If it causes their further use in unsecured http
contexts this could result in a web less safe for users. For that reason it may be desirable to restrict its use, or at least the use of the set
and delete
operations, to secure origins running in secure contexts.
7.3. Surprises
Some existing cookie behavior (especially domain-rather-than-origin orientation, unsecured contexts being able to set cookies readable in secure contexts, and script being able to set cookies unreadable from script contexts) may be quite surprising from a web security standpoint.
Other surprises are documented in Section 1 of Cookies: HTTP State Management Mechanism (RFC 6265bis) - for instance, a cookie may be set for a superdomain (e.g. app.example.com may set a cookie for the whole example.com domain), and a cookie may be readable across all port numbers on a given domain name.
Further complicating this are historical differences in cookie-handling across major browsers, although some of those (e.g. port number handling) are now handled with more consistency than they once were.
7.4. Prefixes
Where feasible the examples use the __Host-
and __Secure-
name prefixes which causes some current browsers to disallow overwriting from unsecured contexts, disallow overwriting with no Secure
flag, and — in the case of __Host-
— disallow overwriting with an explicit Domain
or non-'/' Path
attribute (effectively enforcing same-origin semantics.) These prefixes provide important security benefits in those browsers implementing Secure Cookies and degrade gracefully (i.e. the special semantics may not be enforced in other cookie APIs but the cookies work normally and the async cookies API enforces the secure semantics for write operations) in other browsers. A major goal of this API is interoperation with existing cookies, though, so a few examples have also been provided using cookie names lacking these prefixes.
Prefix rules are also enforced in write operations by this API, but may not be enforced in the same browser for other APIs. For this reason it is inadvisable to rely on their enforcement too heavily until and unless they are more broadly adopted.
7.5. URL scoping
Although a service worker script cannot directly access cookies today, it can already use controlled rendering of in-scope HTML and script resources to inject cookie-monitoring code under the remote control of the service worker script. This means that cookie access inside the scope of the service worker is technically possible already, it’s just not very convenient.
When the service worker is scoped more narrowly than /
it may still be able to read path-scoped cookies from outside its scope’s path space by successfully guessing/constructing a 404 page URL which allows IFRAME-ing and then running script inside it the same technique could expand to the whole origin, but a carefully constructed site (one where no out-of-scope pages are IFRAME-able) can actually deny this capability to a path-scoped service worker today and I was reluctant to remove that restriction without further discussion of the implications.
7.6. Cookie aversion
To reduce complexity for developers and eliminate the need for ephemeral test cookies, this async cookies API will explicitly reject attempts to write or delete cookies when the operation would be ignored. Likewise it will explicitly reject attempts to read cookies when that operation would ignore actual cookie data and simulate an empty cookie jar. Attempts to observe cookie changes in these contexts will still "work", but won’t invoke the callback until and unless read access becomes allowed (due e.g. to changed site permissions.)
Today writing to document.cookie
in contexts where script-initiated cookie-writing is disallowed typically is a no-op. However, many cookie-writing scripts and frameworks always write a test cookie and then check for its existence to determine whether script-initiated cookie-writing is possible.
Likewise, today reading document.cookie
in contexts where script-initiated cookie-reading is disallowed typically returns an empty string. However, a cooperating web server can verify that server-initiated cookie-writing and cookie-reading work and report this to the script (which still sees empty string) and the script can use this information to infer that script-initiated cookie-reading is disallowed.
8. Acknowledgements
Thanks to Benjamin Sittler, who created the initial proposal for this API.
Many thanks to Adam Barth, Alex Russell, Andrea Marchesini, Anne van Kesteren, Ben Kelly, Craig Francis, Daniel Murphy, Domenic Denicola, Elliott Sprehn, Fagner Brack, Jake Archibald, Joel Weinberger, Marijn Kruisselbrink, and Mike West for helping craft this proposal.
Special thanks to Tab Atkins, Jr. for creating and maintaining Bikeshed, the specification authoring tool used to create this document, and for his general authoring advice.