Service Workers

This specification describes a method that enables applications to take advantage of persistent background processing, including hooks to enable bootstrapping of web applications while offline.

The core of this system is an event-driven Web Worker, which responds to events dispatched from documents and other sources. A system for managing installation, versions, and upgrades is provided.

The service worker is a generic entry point for event-driven background processing in the Web Platform that is extensible by other specifications.

Status of This Document

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 http://www.w3.org/TR/.

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.

Client Context

Example: Bootstrapping with a ServiceWorker

// scope defaults to "/"
navigator.serviceWorker.register("/assets/v1/serviceworker.js").then(
  function(registration) {
    console.log("success!");
    if (registration.installing) {
      registration.installing.postMessage("Howdy from your installing page.");
    }
  },
  function(why) {
    console.error("Installing the worker failed!:", why);
  });

3.1

`ServiceWorker`

[Exposed=(Window,Worker)]
interface ServiceWorker : Worker {
  readonly attribute USVString scriptURL;
  readonly attribute ServiceWorkerState state;

  // event
  attribute EventHandler onstatechange;

  // terminate() method inherited from Worker should not be accessible.
};

enum ServiceWorkerState {
  "installing",
  "installed",
  "activating",
  "activated",
  "redundant"
};

A ServiceWorker object represents a service worker. Each ServiceWorker object is associated with a service worker. Multiple separate objects implementing the ServiceWorker interface across document environments and worker environments can all be associated with the same service worker simultaneously.

A ServiceWorker object has an associated ServiceWorkerState object which is itself associated with service worker's state.

The terminate() method inherited from Worker, when called on the context object, should throw an "InvalidAccessError" exception.

The postMessage(message, transfer) method inherited from Worker, when called on the context object, should throw an "InvalidStateError" exception if the state attribute value of the context object is "redundant". Otherwise, it should run a worker, if not running, for a script with its associated service worker serviceWorker's script url and serviceWorker's environment settings object, and run as defined on the Worker interface.

Communication with these workers is provided via standard HTML5 messaging APIs, and messaging occurs as per usual with Web Workers.

3.1.1

`scriptURL`

The scriptURL attribute must return service worker's serialized script url.

For example, consider a document created by a navigation to https://example.com/app.html which matches via the following registration call which has been previously executed:

// Script on the page https://example.com/app.html
navigator.serviceWorker.register("/service_worker.js", { scope: "/" });

The value of navigator.serviceWorker.controller.scriptURL will be "https://example.com/service_worker.js".

3.1.2

`state`

The state attribute must return the value (in ServiceWorkerState enumeration) corresponding to the first matching statement, switching on service worker's state:

installing: "installing"
The service worker in this state is considered an installing worker. During this state, event.waitUntil(f) can be called inside the oninstall event handler to extend the life of the installing worker until the passed promise resolves successfully. This is primarily used to ensure that the service worker is not active until all of the core caches are populated.
installed: "installed"
The service worker in this state is considered a waiting worker.
activating: "activating"
The service worker in this state is considered an active worker. During this state, event.waitUntil(f) can be called inside the onactivate event handler to extend the life of the active worker until the passed promise resolves successfully. No functional events are dispatched until the state becomes activated.
activated: "activated"
The service worker in this state is considered an active worker ready to handle functional events.
redundant: "redundant"
A new service worker is replacing the current service worker, or the current service worker is being discarded due to an install failure.

3.1.3

Event handler

The following is the event handler (and its corresponding event handler event type) that must be supported, as event handler IDL attributes, by all objects implementing ServiceWorker interface:

event handler	event handler event type
`onstatechange`	`statechange`

3.2

`ServiceWorkerRegistration`

[Exposed=(Window,Worker)]
interface ServiceWorkerRegistration : EventTarget {
  [Unforgeable] readonly attribute ServiceWorker? installing;
  [Unforgeable] readonly attribute ServiceWorker? waiting;
  [Unforgeable] readonly attribute ServiceWorker? active;

  readonly attribute USVString scope;

  void update();
  Promise<boolean> unregister();

  // event
  attribute EventHandler onupdatefound;
};

A ServiceWorkerRegistration object represents a service worker registration. Each ServiceWorkerRegistration object is associated with a service worker registration (a service worker registration). Multiple separate objects implementing the ServiceWorkerRegistration interface across document environments and worker environments can all be associated with the same service worker registration simultaneously.

A ServiceWorkerRegistration has an associated service worker client (a service worker client).

3.2.1

`installing`

installing attribute must return a ServiceWorker object that represents the installing worker.

3.2.2

`waiting`

waiting attribute must return a ServiceWorker object that represents the waiting worker.

3.2.3

`active`

active attribute must return a ServiceWorker object that represents the active worker.

3.2.4

`scope`

The scope attribute must return service worker registration's serialized scope url.

In the example in section 3.1.1, the value of registration.scope, obtained from navigator.serviceWorker.ready.then(function(registration) { console.log(registration.scope); }) for example, will be "https://example.com/".

3.2.5

`update()`

update() pings the server for an updated version of this script without consulting caches. This is conceptually the same operation that UA does maximum once per every 24 hours.

update() method must run these steps or their equivalent:

Invoke Soft Update algorithm, or its equivalent, passing the service worker registration registration as the argument.

3.2.6

`unregister()`

The unregister() method unregisters the service worker registration. It is important to note that the currently controlled service worker client's active worker's containing service worker registration is effective until all the service worker clients (including itself) using this service worker registration unload. That is, unregister() method only affects subsequent navigations.

unregister() method must return the result of running these steps or their equivalent:

Let scopeURL be the scope url of the service worker registration.
Return the result of running the Unregister algorithm, or its equivalent, passing the service worker client client, and scopeURL as the arguments.

3.2.7

Event handler

The following is the event handler (and its corresponding event handler event type) that must be supported, as event handler IDL attributes, by all objects implementing ServiceWorkerRegistration interface:

event handler	event handler event type
`onupdatefound`	`updatefound`

3.3

`navigator.serviceWorker`

partial interface Navigator {
  readonly attribute ServiceWorkerContainer serviceWorker;
};

partial interface WorkerNavigator {
  readonly attribute ServiceWorkerContainer serviceWorker;
};

The serviceWorker attribute must return the ServiceWorkerContainer object for the context object.

3.4

`ServiceWorkerContainer`

[Exposed=(Window,Worker)]
interface ServiceWorkerContainer : EventTarget {
  [Unforgeable] readonly attribute ServiceWorker? controller;
  readonly attribute Promise<ServiceWorkerRegistration> ready;

  Promise<ServiceWorkerRegistration> register(USVString scriptURL, optional RegistrationOptions options);

  Promise<ServiceWorkerRegistration> getRegistration(optional USVString clientURL = "");
  Promise<sequence<ServiceWorkerRegistration>?> getRegistrations();


  // events
  attribute EventHandler oncontrollerchange;
  attribute EventHandler onerror;
};

dictionary RegistrationOptions {
  USVString scope;
};

A ServiceWorkerContainer provides capabilities to register, unregister, and update the service worker registrations, and provides access to the state of the service worker registrations and their associated service workers.

A ServiceWorkerContainer has an associated service worker client, which is a service worker client whose global object is associated with the Navigator object or the WorkerNavigator object that the ServiceWorkerContainer is retrieved from.

A ServiceWorkerContainer object has an associated ready promise (a promise). It is initially set to null.

3.4.1

`controller`

controller attribute must return a ServiceWorker object that represents the context object's service worker client's active worker.

navigator.serviceWorker.controller returns null if the request is a force refresh (shift+refresh).

3.4.2

`ready`

ready attribute must return the result of running these steps or their equivalent:

If the context object's ready promise is null, then:
1. Set the context object's ready promise to a new promise.
If the context object's ready promise is settled, then:
1. Return the context object's ready promise.
Let registration be null.
Let clientURL be the context object's service worker client's creation url.
Run the following substeps in parallel:
1. CheckRegistration: If the result of running Match Service Worker Registration algorithm, or its equivalent, with clientURL as its argument is not null, then:
  1. Set registration to the result value.
2. Else:
  1. Wait until scope to registration map has a new entry.
  2. Jump to the step labeled CheckRegistration.
3. If registration's active worker is null, then:
  1. Wait until registration's active worker changes.
  Implementers should consider this condition is met when the corresponding registration request gets to the step 1.8 of Activate algorithm.
4. Resolve context object's ready promise with a ServiceWorkerRegistration object, setting its service worker client to service worker client, which represents registration.
Return context object's ready promise.

The ready attribute is designed in a way that the returned promise will never reject. Instead, it waits until the promise resolves with a service worker registration that has an active worker.

3.4.3

`register(scriptURL, options)`

The register(scriptURL, options) method creates or updates a service worker registration for the given scope url. If successful, a service worker registration ties the provided script url to a scope url, which is subsequently used for navigation matching.

register(scriptURL, options) method must return the result of running these steps or their equivalent:

Let scriptURL be the result of parsing scriptURL with entry settings object's API base URL.
If scriptURL is failure, return a promise rejected with a TypeError.
Let scopeURL be null.
If the optional argument options is omitted or options.scope is not present, set scopeURL to the result of parsing a string "./" with scriptURL.
The scope url for the registration is set to the location of the service worker script by default.
Else, set scopeURL to the result of parsing options.scope with entry settings object's API base URL.
If scopeURL is failure, return a promise rejected with a TypeError.
Return the result of running the Register algorithm, or its equivalent, passing the service worker client client, scriptURL, scopeURL as the arguments.

3.4.4

`getRegistration(clientURL)`

getRegistration(clientURL) method must run these steps or their equivalent:

Let clientURL be the result of parsing clientURL with entry settings object's API base URL.
If clientURL is failure, return a promise rejected with a TypeError.
If the origin of clientURL is not the context object's service worker client's origin, return a promise with a "SecurityError" exception.
Let promise be a new promise.
Run the following substeps in parallel:
1. Let registration be the result of running Match Service Worker Registration algorithm, or its equivalent, with clientURL as its argument.
2. If registration is not null, then:
  1. Resolve promise with a ServiceWorkerRegistration object, setting its service worker client to service worker client, which represents registration.
3. Else:
  1. Resolve promise with undefined.
Return promise.

3.4.5

`getRegistrations()`

getRegistrations() method must run these steps or their equivalent:

Let promise be a new promise.
Run the following substeps in parallel:
1. Let array be an empty array.
2. For each Record {[[key]], [[value]]} entry of its scope to registration map:
  1. If the origin of the result of parsing entry.[[key]] is its service worker client's origin, then:
    1. Add a ServiceWorkerRegistration object, setting its service worker client to service worker client, associated with entry.[[value]] to the array.
3. Resolve promise with array.
Return promise.

3.4.6

Event handlers

The following are the event handlers (and its corresponding event handler event types) that must be supported, as event handler IDL attributes, by all objects implementing the ServiceWorkerContainer interface:

event handler	event handler event type
`oncontrollerchange`	`controllerchange`
`onerror`	`error`

3.5

Events

The following events are dispatched on ServiceWorker object:

Event name	Interface	Dispatched when…
`statechange`	`Event`	The `state` attribute of the `ServiceWorker` object is changed.

The following events are dispatched on ServiceWorkerContainer object:

Event name	Interface	Dispatched when…
`updatefound`	`Event`	The service worker registration's installing worker changes (See step 4.6 of the Install algorithm).
`controllerchange`	`Event`	The service worker client's active worker changes. (See step 1.10 of the Activate algorithm. The skip waiting flag of a service worker causes activation of the service worker registration to occur while service worker clients are using the service worker registration, `navigator.serviceWorker.controller` immediately reflects the active worker as the service worker that controls the service worker client.)
`error`	`ErrorEvent`	Any error occurred from the associated service workers.

Execution Context

Example: Serving Cached Resources

// caching.js
this.addEventListener("install", function(e) {
  e.waitUntil(
    // Open a cache of resources.
    caches.open("shell-v1").then(function(cache) {
      // Begins the process of fetching them.
      // The coast is only clear when all the resources are ready.
      return cache.addAll([
        "/app.html",
        "/assets/v1/base.css",
        "/assets/v1/app.js",
        "/assets/v1/logo.png",
        "/assets/v1/intro_video.webm"
      ]);
    })
  );
});

this.addEventListener("fetch", function(e) {
  // No "fetch" events are dispatched to the service worker until it
  // successfully installs and activates.

  // All operations on caches are async, including matching URLs, so we use
  // promises heavily. e.respondWith() even takes promises to enable this:
  e.respondWith(
    caches.match(e.request).then(function(response) {
      return response || e.default();
    }).catch(function() {
      return caches.match("/fallback.html");
    })
  );
});

4.1

`ServiceWorkerGlobalScope`

[Global=(Worker,ServiceWorker), Exposed=ServiceWorker]
interface ServiceWorkerGlobalScope : WorkerGlobalScope {
  readonly attribute Cache scriptCache;

  // A container for a list of Client objects that correspond to
  // browsing contexts (or shared workers) that are on the origin of this SW
  readonly attribute Clients clients;
  readonly attribute ServiceWorkerRegistration registration;

  Promise<void> skipWaiting();

  attribute EventHandler oninstall;
  attribute EventHandler onactivate;
  attribute EventHandler onfetch;
  attribute EventHandler onbeforeevicted;
  attribute EventHandler onevicted;

  // The event.source of these MessageEvents are instances of Client
  attribute EventHandler onmessage;

  // close() method inherited from WorkerGlobalScope should not be accessible.
};

A ServiceWorkerGlobalScope object represents the global execution context of a service worker. A ServiceWorkerGlobalScope object has an associated service worker (a service worker).

ServiceWorkerGlobalScope object provides generic, event-driven, time-limited script execution contexts that run at an origin. Once successfully registered, a service worker is started, kept alive and killed by their relationship to events, not service worker clients. Any type of synchronous requests must not be initiated inside of a service worker.

The close() method inherited from WorkerGlobalScope, when called on the context object, should throw an "InvalidAccessError" exception.

4.1.1

`scriptCache`

scriptCache must return a Cache object that represents the storage for scripts that are cached as part of the service worker installation.

4.1.2

`clients`

clients attribute must return the Clients object.

4.1.3

`registration`

The registration attribute must return the ServiceWorkerRegistration object that represents the service worker's containing service worker registration.

4.1.4

`skipWaiting()`

The skipWaiting() method allows this service worker to progress from the registration's waiting position to active even while service worker clients are using the registration.

skipWaiting() method must run these steps or their equivalent:

Let promise be a new promise.
Run the following substeps in parallel:
1. Set service worker's skip waiting flag
2. If service worker's state is installed, then:
  1. Run Activate algorithm, or its equivalent, passing service worker's registration as the argument.
3. Resolve promise with undefined.
Return promise.

4.1.5

Event handlers

event handler	event handler event type
`oninstall`	`install`
`onactivate`	`activate`
`onfetch`	`fetch`
`onbeforeevicted`	`beforeevicted`
`onevicted`	`evicted`
`onmessage`	`message`

For onmessage event handler, ServiceWorkerGlobalScope objects act as if they had an implicit MessagePort associated with them. This port is part of a channel that is set up when the service worker is spun off to run, but it is not exposed. This object must never be garbage collected before the ServiceWorkerGlobalScope object. All messages received by that port must immediately be retargeted at the ServiceWorkerGlobalScope object. That is, an event named message using the MessageEvent interface is dispatched on ServiceWorkerGlobalScope object. The event.source of these MessageEvents are instances of Client.

4.2

`Client`

[Exposed=ServiceWorker]
interface Client {
  readonly attribute USVString url;
  void postMessage(any message, optional sequence<Transferable> transfer);
};

[Exposed=ServiceWorker]
interface WindowClient : Client {
  readonly attribute VisibilityState visibilityState;
  readonly attribute boolean focused;
  readonly attribute FrameType frameType;
  Promise<WindowClient> focus();
};

enum FrameType {
  "auxiliary",
  "top-level",
  "nested",
  "none"
};

A Client object has an associated service worker client (a service worker client).

A WindowClient object has an associated visibility state, which is one of visibilityState attribute value.

A WindowClient object has an associated focus state, which is either true or false. (Initially false).

4.2.1

`url`

The url attribute must return the context object's associated service worker client's serialized creation url.

4.2.2

`visibilityState`

The visibilityState attribute must return the context object's visibility state.

4.2.3

`focused`

The focused attribute must return the context object's focus state.

4.2.4

`frameType`

The frameType attribute must return the value (in FrameType enumeration) corresponding to the first matching statement, switching on service worker client's frame type:

auxiliary: "auxiliary"
The window client's global object's browsing context is an auxiliary browsing context.
top-level: "top-level"
The window client's global object's browsing context is a top-level browsing context.
nested: "nested"
The window client's global object's browsing context is a nested browsing context.
none: "none"

4.2.5

`focus()`

The focus() method must run these steps or their equivalent:

If this algorithm is not allowed to show a popup, return a promise rejected with an "InvalidAccessError" exception.
Let promise be a new promise.
Run these steps in parallel:
1. Let browsingContext be the context object's associated service worker client's global object's browsing context.
2. Queue a task to run the following substeps on the context object's associated service worker client's responsible event loop using the user interaction task source:
  1. Run the focusing steps with browsingContext.
  2. Resolve promise with the result of running Capture Window Client algorithm, or its equivalent, with browsingContext as the argument.
Return promise.

4.3

`Clients`

[Exposed=ServiceWorker]
interface Clients {
  // The objects returned will be new instances every time
  Promise<sequence<Client>?> getAll(optional ClientQueryOptions options);
  Promise<WindowClient> openWindow(USVString url);
  Promise<void> claim();
};

dictionary ClientQueryOptions {
  boolean includeUncontrolled = false;
  ClientType type = "window";
};

enum ClientType {
  "window",
  "worker",
  "sharedworker",
  "all"
};

The Clients interface represents a container for a list of Client objects.

4.3.1

`getAll(options)`

The getAll(options) method must run these steps or their equivalent:

Let promise be a new promise.
Run these steps in parallel:
1. Let clients be an empty array.
2. If the optional argument options is omitted, then:
  1. For each service worker client client whose active worker is the associated service worker, in the most recently focused order for window clients:
    1. If client is a window client, then:
      1. Let windowClient be the result of running Capture Window Client algorithm, or its equivalent, with client's responsible browsing context as the argument.
      2. Add windowClient to clients.
  2. Resolve promise with clients.
3. Else:
  1. Let targetClients be an empty array.
  2. For each service worker client client whose origin is the same as the associated service worker's origin:
    1. If options.includeUncontrolled is false, then:
      1. If client's active worker is the associated service worker, add client to targetClients.
    2. Else:
      1. Add client to targetClients.
  3. Let matchedClients be an empty array.
  4. For each service worker client client in targetClients, in the most recently focused order for window clients:
    1. If options.type is "window", and client is a window client, then:
      1. Let windowClient be the result of running Capture Window Client algorithm, or its equivalent, with client's responsible browsing context as the argument.
      2. Add windowClient to matchedClients.
    2. Else if options.type is "worker" and client is a dedicated worker client, add a Client object that represents client to matchedClients.
    3. Else if options.type is "sharedworker" and clientis a shared worker client, add a Client object that represents client to matchedClients.
    4. Else if options.type is "all", then:
      1. If client is a window client, then:
        
        Let windowClient be the result of running Capture Window Client algorithm, or its equivalent, with client's responsible browsing context as the argument.
        
        Add windowClient to matchedClients.
      2. Else, add a Client object that represents client to matchedClients.
  5. Resolve promise with matchedClients.
Return promise.

4.3.2

`openWindow(url)`

The openWindow(url) method must run these steps or their equivalent:

Let url be the result of parsing url with entry settings object's API base URL.
If url is failure, return a promise rejected with a TypeError.
If this algorithm is not allowed to show a popup, return a promise rejected with an "InvalidAccessError" exception.
Let promise be a new promise.
Run these steps in parallel:
1. Let newContext be a new top level browsing context.
2. If url is about:blank, then:
  1. Queue a task to fire a simple event named load at newContext's Window object, with target override set to newContext's Window object's Document object.
3. Otherwise:
  1. Navigate newContext to url, with exceptions enabled and replacement enabled.
4. If the origin of url is not client's origin, then:
  1. Resolve promise with null.
  2. Abort these steps.
5. Let client be the result of running Capture Window Client algorithm, or its equivalent, with newContext as the argument.
6. Resolve promise with client.
Return promise.

4.3.3

`claim()`

The claim() method must run these steps or their equivalent:

If the service worker is not an active worker, return a promise rejected with an "InvalidStateError" exception.
Let promise be a new promise.
Run the following substeps in parallel:
1. For each service worker client client whose origin is the same as the service worker's origin:
  1. Let registration be the result of running Match Service Worker Registration algorithm passing client's creation url as the argument.
  2. If registration is not the service worker's containing service worker registration, continue to the next iteration of the loop.
  3. If client's active worker is not the service worker, then:
    1. Set client's active worker to service worker.
    2. Queue a task to fire a simple event named controllerchange at the ServiceWorkerContainer object client is associated with.
2. Resolve promise with undefined.
Return promise.

4.4

`ExtendableEvent`

[Constructor(DOMString type, optional ExtendableEventInit eventInitDict), Exposed=ServiceWorker]
interface ExtendableEvent : Event {
  void waitUntil(Promise<any> f);
};

dictionary ExtendableEventInit : EventInit {
  // Defined for the forward compatibility across the derived events
};

Service workers have two lifecycle events, install and activate. Service workers use the ExtendableEvent interface for activate event and the InstallEvent interface, which inherits from the ExtendableEvent interface, for install event. Service worker extensions that define event handlers may also use the ExtendableEvent interface.

An ExtendableEvent object has an associated extend lifetime promises (an array of promises). It is initially set to null.

The service worker should not be terminated until the result of waiting for all of the extend lifetime promises has been settled. However, the user agent may impose a time limit to this lifetime extension.

4.4.1

`event.waitUntil(f)`

waitUntil(f) method, extends the lifetime of the event. When called in oninstall, it delays treating the installing worker as installed (i.e. a waiting worker) until the passed promise resolves successfully. This is primarily used to ensure that a service worker is not considered installed (i.e. a waiting worker) until all of the core caches it depends on are populated. When called in onactivate, it delays treating the active worker as activated until the passed promise resolves successfully. This is primarily used to ensure that any functional events are not dispatched to the ServiceWorkerGlobalScope object that represents the service worker until it upgrades database schemas and deletes the outdated cache entries. Service worker extensions that define event handlers will define their own behaviours, allowing the extend lifetime promises to suggest operation length, and the rejected state of any of the promise in extend lifetime promises to suggest operation failure.

waitUntil(f) method must run these steps or their equivalent:

If the active function is not the callback of the event handler whose type is the context object's type value, then:
1. Throw an "InvalidStateError" exception.
2. Abort these steps.
Add f to extend lifetime promises.

4.5

`InstallEvent`

[Constructor(DOMString type, optional InstallEventInit eventInitDict), Exposed=ServiceWorker]
interface InstallEvent : ExtendableEvent {
  readonly attribute ServiceWorker? activeWorker;
};

dictionary InstallEventInit : EventInit {
  ServiceWorker activeWorker;
};

4.6

`FetchEvent`

[Constructor(DOMString type, optional FetchEventInit eventInitDict), Exposed=ServiceWorker]
interface FetchEvent : Event {
  readonly attribute Request request;
  readonly attribute Client client;
  readonly attribute boolean isReload;

  void respondWith((Response or Promise<Response>) r);
  Promise<Response> forwardTo(USVString url);
  Promise<Response> default();
};

dictionary FetchEventInit : EventInit {
  Request request;
  Client client;
  boolean isReload;
};

Each event using FetchEvent interface has the following associated flag that is initially unset:

wait to respond flag
respond-with entered flag
respond-with error flag

4.6.1

`event.respondWith(r)`

When event.respondWith(r) method is invoked, the argument, r, must resolve with a Response, else a network error is returned to Fetch. If the request is a top-level navigation and the return value is a Response whose type attribute is "opaque" (i.e., an opaque response body), a network error is returned to Fetch. The final URL of all successful (non network-error) responses is the requested URL. Renderer-side security checks about tainting for cross-origin content are tied to the transparency (or opacity) of the Response body, not URLs.

respondWith(r) method must run these steps or their equivalent:

If the active function is not the callback of the event handler whose type is fetch, then:
1. Throw an "InvalidStateError" exception.
2. Abort these steps.
If the respond-with entered flag is set, then:
1. Throw an "InvalidStateError" exception.
2. Abort these steps.
Set the stop propagation flag and stop immediate propagation flag.
Set the respond-with entered flag.
Set the wait to respond flag.
Let responsePromise be null.
If r is a Response object, then:
1. Set responsePromise to a promise resolved with r.
Else:
1. Set responsePromise to r.
Run the following substeps in parallel:
1. Wait until responsePromise settles.
2. If responsePromise rejected, then:
  1. Set the respond-with error flag.
3. If responsePromise resolved with response, then:
  1. If response is a Response object, then:
    1. Let request be the context object's request attribute value.
    2. If response.type is "opaque", and request's associated request is a client request, set the respond-with error flag.
    3. If response's body is non-null, then:
      1. If response's used flag is set, set the respond-with error flag.
      2. Set response's used flag.
  2. Else:
    1. Set the respond-with error flag.
    If the respond-with error flag is set, a network error is returned to Fetch through Handle Fetch algorithm. (See the step 19.1.) Otherwise, the value response is returned to Fetch through Handle Fetch algorithm. (See the step 20.1.)
4. Unset the wait to respond flag.

4.6.2

`event.default()`

The invocation of event.default() method performs a fetch using event.request. event.request represents the original request from the controlled service worker client. During the execution, the original request is not altered (except the skip service worker flag), and thus event.default() fetches the original request through the UA's HTTP stack. event.default() returns a promise, which resolves with a Response object, that can be an argument to the event.respondWith(r) method.

default() method must run these steps or their equivalent:

If event's dispatch flag is unset, then:
1. Return a promise rejected with an "InvalidStateError" exception.
Let promise be a new promise.
Run the following substeps in parallel:
1. Let r be the context object's request attribute value.
2. If r's body is non-null, then:
  1. If r's used flag is set, then:
    1. Reject promise with a TypeError.
    2. Abort these steps.
  2. Set r's used flag.
3. Let request be r's associated request.
4. Set request's skip service worker flag and request's synchronous flag.
5. Let response be the result of running fetch with request as its argument.
6. If response is a network error, then:
  1. Reject promise with a TypeError.
7. Else:
  1. Resolve promise with a new Response object associated with response.
Return promise.

4.6.3

`event.isReload`

isReload attribute must return true if event was dispatched with the user's intention for the page reload, and false otherwise. Pressing the refresh button should be considered a reload while clicking a link and pressing the back button should not. The behavior of the Ctrl+l enter is left to the implementations of the user agents.

4.7

Events

The following events are dispatched on ServiceWorkerGlobalScope object:

Event name	Interface	Dispatched when…
`install`	`InstallEvent`	[Lifecycle event] The service worker's containing service worker registration's installing worker changes. (See step 4.7.3 of the Install algorithm.)
`activate`	`ExtendableEvent`	[Lifecycle event] The service worker's containing service worker registration's active worker changes. (See step 1.11.3 of the Activate algorithm.)
`fetch`	`FetchEvent`	[Functional event] Fetch invokes Handle Fetch with `request`. As a result of performing Handle Fetch, the Service Woker returns a response to Fetch. The response, represented by a `Response` object, can be retrieved from a Cache object or directly from network using `self.fetch(input, init)` method or `event.default()` method. (A custom `Response` object can be another option.)

Custom event types for beforeevicted and evicted should be added.

Caches

To allow authors to fully manage their content caches for offline use, the Window and the WorkerGlobalScope provide the caching methods largely conforming to ECMAScript 6 Map objects with additional convenience methods. An origin can have multiple, named Cache objects, whose contents are entirely under the control of scripts. Caches are not shared across origins, and they are completely isolated from the browser's HTTP cache.

5.1

Constructs

A fetching record is a Record {[[key]], [[value]]} where [[key]] is a Request and [[value]] is a Response.

A fetching record has an associated incumbent record (a fetching record). It is initially set to null.

A request to response map is a List of fetching records.

A name to cache map is a List of the Record {[[key]], [[value]]} where [[key]] is a string that represents a name of the Cache object and [[value]] is a Cache object.

Each origin has an associated name to cache map.

5.2

Understanding Cache Lifetimes

The Cache instances are not part of the browser's HTTP cache. The Cache objects are exactly what authors have to manage themselves. The Cache objects do not get updated unless authors explicitly request them to be. The Cache objects do not expire unless authors delete the entries. The Cache objects do not disappear just because the service worker script is updated. That is, caches are not updated automatically. Updates must be manually managed. This implies that authors should version their caches by name and make sure to use the caches only from the version of the service worker that can safely operate on.

5.3

`self.caches`

partial interface Window {
  readonly attribute CacheStorage caches;
};

partial interface WorkerGlobalScope {
  readonly attribute CacheStorage caches;
};

5.3.1

`caches`

caches attribute must return a CacheStorage object that represents the name to cache map of the context object's environment settings object's origin.

5.4

`Cache`

[Exposed=(Window,Worker)]
interface Cache {
  Promise<Response> match(RequestInfo request, optional CacheQueryOptions options);
  Promise<sequence<Response>> matchAll(optional RequestInfo request, optional CacheQueryOptions options);
  Promise<void> add(RequestInfo request);
  Promise<void> addAll(sequence<RequestInfo> requests);
  Promise<void> put(RequestInfo request, Response response);
  Promise<boolean> delete(RequestInfo request, optional CacheQueryOptions options);
  Promise<sequence<Request>> keys(optional RequestInfo request, optional CacheQueryOptions options);
};

dictionary CacheQueryOptions {
  boolean ignoreSearch = false;
  boolean ignoreMethod = false;
  boolean ignoreVary = false;
  boolean prefixMatch = false;
  DOMString cacheName;
};

dictionary CacheBatchOperation {
  DOMString type;
  Request request;
  Response response;
  CacheQueryOptions options;
};

A Cache object represents a request to response map. Multiple separate objects implementing the Cache interface across document environments and worker environments can all be associated with the same request to response map simultaneously.

Cache objects are always enumerable via self.caches in insertion order (per ECMAScript 6 Map objects.)

5.4.1

`match(request, options)`

match(request, options) method must run these steps or their equivalent:

Let promise be a new promise.
Run these steps in parallel:
1. Let p be the result of running the algorithm specified in matchAll(request, options) method with request and options as the arguments.
2. Wait until p settles.
3. If p rejects with an exception, then:
  1. Reject promise with that exception.
4. Else if p resolves with an array, responseArray, then:
  1. If responseArray is an empty array, then:
    1. Resolve promise with undefined.
  2. Else:
    1. Resolve promise with the first element of responseArray.
Return promise.

5.4.2

`matchAll(request, options)`

matchAll(request, options) method must run these steps or their equivalent:

Let promise be a new promise.
Run these steps in parallel:
1. Let responseArray be an empty array.
2. If the optional argument request is omitted, then:
  1. For each fetching record entry of its request to response map, in key insertion order:
    1. Add entry.[[value]] to responseArray.
  2. Resolve promise with responseArray.
  3. Abort these steps.
3. Else:
  1. Let r be null.
  2. If request is a USVString, then:
    1. Set r to the associated request of the result of invoking the initial value of Request as constructor with request as its argument. If this throws an exception, return a promise rejected with that exception.
  3. Else:
    1. Set r to request's associated request.
  4. Set r's url's fragment to null.
  5. Let entries be the result of running Query Cache algorithm passing a Request object that represents r and options as the arguments.
  6. For each entry of entries:
    1. If the incumbent record incumbentRecord of the corresponding fetching record fetchingRecord in request to response map is not null, add incumbentRecord.[[value]] to responseArray.
    2. Else, add entry[1] to responseArray.
  7. Resolve promise with responseArray.
Return promise.

5.4.3

`add(request)`

add(request) method must run these steps or their equivalent:

Let requests be an array containing only request.
Set responseArrayPromise to the result of running the algorithm specified in addAll(requests) passing requests as the argument.
Let p be transforming responseArrayPromise with onFulfilled.
Upon fulfillment of p with value responseArray, perform the following substeps, onFulfilled, in parallel:
1. Resolve p with undefined.
Return p.

5.4.4

`addAll(requests)`

addAll(requests) method must run these steps or their equivalent:

Let responsePromiseArray be an empty array.
Let requestArray be an empty array.
For each request in requests:
1. Let r be null.
2. If request is a USVString, then:
  1. Set r to the associated request of the result of invoking the initial value of Request as constructor with request as its argument. If this throws an exception, return a promise rejected with that exception.
3. Else:
  1. If request's body is non-null, then:
    1. If request's used flag is set, return a promise rejected with a TypeError.
    2. Set request's used flag.
  2. Set r to request's associated request.
4. Set r's url's fragment to null.
5. Add a Request object that represents r to requestArray.
6. If r's url's scheme is not one of "http" and "https", then:
  1. Add a promise rejected with a "NetworkError" exception to responsePromiseArray.
  2. Continue to the next iteration of the loop.
7. Let responsePromise be a new promise.
8. Run the following in parallel:
  - Fetch r.
  - To process response for response, run these substeps:
    1. If response's type is error, reject responsePromise with a TypeError.
    2. Else, resolve responsePromise with new Response object associated with response.
    This step ensures that the promise for this fetch resolves as soon as the response's headers become available.
  - To process response body for response, do nothing.
  - To process response end-of-file for response, do nothing.
9. Add responsePromise to responsePromiseArray.
Let p be waiting for all of responsePromiseArray.
Let q be transforming p with onFulfilled.
Upon fulfillment of p with value responseArray, perform the following substeps, onFulfilled, in parallel:
1. Let operations be an empty array.
2. For each response in responseArray with the index index:
  1. If response's body is non-null, then:
    1. If response's used flag is set, reject q with a TypeError.
    2. Set response's used flag.
  2. Let o be an empty object representing a CacheBatchOperation dictionary.
  3. Set the type dictionary member of o to "put".
  4. Set the request dictionary member of o to requestArray[index].
  5. Set the response dictionary member of o to response.
  6. Add o to operations.
3. Let resultPromise to the result of running Batch Cache Operations algorithm passing operations as the argument.
4. Upon fulfillment of resultPromise with value responses, perform the following substeps, onFulfilled, in parallel:
  1. For each response in responses:
    1. Let responseBodyPromise be a new promise.
    2. Run the following substeps in parallel:
      1. Wait for either end-of-file to have been pushed to response's associated response r's body or for r to have a termination reason.
      2. If r had a termination reason, then:
        
        If the incumbent record incumbentRecord of the corresponding fetching record fetchingRecord in request to response map is not null, then:
        
        Set fetchingRecord in request to response map to the copy of incumbentRecord.
        
        Else:
        
        Delete fetchingRecord from request to response map.
        
        Reject responseBodyPromise with a TypeError.
      3. Else:
        
        Set the incumbent record of the corresponding fetching record fetchingRecord in request to response map to the copy of fetchingRecord.
        
        Let invalidRecords be the result of running Query Cache algorithm passing fetchingRecord.[[key]] as the argument.
        
        For each invalidRecord in invalidRecords:
        
        If invalidRecord is not fetchingRecord, delete it from request to response map.
        
        Resolve responseBodyPromise with response.
    3. Add responseBodyPromise to responseBodyPromiseArray.
  2. Upon fulfillment of waiting for all of responseBodyPromiseArray, resolve q with undefined.
Return q.

5.4.5

`put(request, response)`

put(request, response) method must run these steps or their equivalent:

Let r be null.
If request is a USVString, then:
1. Set r to the associated request of the result of invoking the initial value of Request as constructor with request as its argument. If this throws an exception, return a promise rejected with that exception.
Else:
1. If request's body is non-null, then:
  1. If request's used flag is set, return a promise rejected with a TypeError.
  2. Set request's used flag.
2. Set r to request's associated request.
Set r's url's fragment to null.
If response's body is non-null, then:
1. If response's used flag is set, return a promise rejected with a TypeError.
2. Set response's used flag.
Let operations be an empty array.
Let o be an empty object representing a CacheBatchOperation dictionary.
Set the type dictionary member of o to "put".
Set the request dictionary member of o to a Request object that represents r.
Set the response dictionary member of o to response.
Add o to operations.
Let resultPromise to the result of running Batch Cache Operations passing operations as the argument.
Let p be transforming resultPromise with onFulfilled.
Upon fulfillment of resultPromise with value responses, perform the following substeps, onFulfilled, in parallel:
1. Wait for either end-of-file to have been pushed to responses[0]'s associated response r's body or for r to have a termination reason.
2. If r had a termination reason, then:
  1. If the incumbent record incumbentRecord of the corresponding fetching record fetchingRecord in request to response map is not null, then:
    1. Set fetchingRecord in request to response map to the copy of incumbentRecord.
  2. Else:
    1. Delete fetchingRecord from request to response map.
  3. Reject p with a TypeError.
3. Else:
  1. Set the incumbent record of the corresponding fetching record fetchingRecord in request to response map to the copy of fetchingRecord.
  2. Let invalidRecords be the result of running Query Cache algorithm passing fetchingRecord.[[key]] as the argument.
  3. For each invalidRecord in invalidRecords:
    1. If invalidRecord is not fetchingRecord, delete it from request to response map.
  4. Resolve p with undefined.
Return p.

5.4.6

`delete(request, options)`

delete(request, options) method must run these steps or their equivalent:

Let r be null.
If request is a USVString, then:
1. Set r to the associated request of the result of invoking the initial value of Request as constructor with request as its argument. If this throws an exception, return a promise rejected with that exception.
Else:
1. Set r to request's associated request.
Set r's url's fragment to null.
Let operations be an empty array.
Let o be an empty object representing a CacheBatchOperation dictionary.
Set the type dictionary member of o to "delete".
Set the request dictionary member of o to a Request object that represents r.
Set the options dictionary member of o to options.
Add o to operations.
Let resultPromise to the result of running Batch Cache Operations passing operations as the argument.
Let p be transforming resultPromise with onFulfilled.
Upon fulfillment of p with responseArray, perform the following substeps, onFulfilled, in parallel:
1. If responseArray is not null, then:
  1. Resolve p with true.
2. Else:
  1. Resolve p with false.
Return p.

5.4.7

`keys(request, options)`

keys(request, options) method must run these steps or their equivalent:

Let promise be a new promise.
Run these steps in parallel:
1. Let resultArray be an empty array.
2. If the optional argument request is omitted, then:
  1. For each fetching record entry of its request to response map, in key insertion order:
    1. Add entry.[[key]] to resultArray.
3. Else:
  1. Let r be null.
  2. If request is a USVString, then:
    1. Set r to the associated request of the result of invoking the initial value of Request as constructor with request as its argument. If this throws an exception, return a promise rejected with that exception.
  3. Else:
    1. Set r to request's associated request.
  4. Set r's url's fragment to null.
  5. Let requestResponseArray be the result of running Query Cache algorithm passing a Request object that represents r and options as the arguments.
  6. For each requestResponse in requestResponseArray:
    1. Add requestResponse[0] to resultArray.
4. Resolve promise with resultArray.
Return promise.

5.5

`CacheStorage`

[Exposed=(Window,Worker)]
interface CacheStorage {
  Promise<Response> match(RequestInfo request, optional CacheQueryOptions options);
  Promise<boolean> has(DOMString cacheName);
  Promise<Cache> open(DOMString cacheName);
  Promise<boolean> delete(DOMString cacheName);
  Promise<sequence<DOMString>> keys();
};

CacheStorage interface is designed to largely conform to ECMAScript 6 Map objects but entirely async, and with additional convenience methods. The methods, clear, forEach, entries and values, are intentionally excluded from the scope of the first version resorting to the ongoing discussion about the async iteration by TC39.

A CacheStorage object represents a name to cache map. Multiple separate objects implementing the CacheStorage interface across document environments and worker environments can all be associated with the same name to cache map simultaneously.

5.5.1

`match(request, options)`

match(request, options) method must run these steps or their equivalent:

Let cacheName be null.
If the optional argument options is not omitted, then:
1. Set cacheName to options.cacheName.
If cacheName is not null, then:
1. Return a promise, p, resolved with the result of running the following substeps:
  1. For each Record {[[key]], [[value]]} entry of its name to cache map, in key insertion order:
    1. If cacheName matches entry.[[key]], then:
      1. Resolve p with the result of running the algorithm specified in match(request, options) method of Cache interface with request and options as the arguments (providing entry.[[value]] as thisArgument to the [[Call]] internal method of match(request, options).)
      2. Abort these steps.
  2. Reject p with an "NotFoundError" exception.
Else:
1. Set p to transforming the result of running the algorithm specified in keys() method, with onFulfilled.
2. Upon fulfillment of p with value keys, perform the following substeps, onFulfilled, in parallel:
  1. For each key in keys:
    1. Let q be the result of running the algorithm specified in match(request, options) method of Cache interface with request and options as the arguments (providing key as thisArgument to the [[Call]] internal method of match(request, options).)
    2. Upon fulfillment of q with value matchedResponse:
      1. If matchedResponse is not undefined, then:
        
        Resolve p with matchedResponse.
        
        Abort these steps.
    3. Upon rejection of q with value err:
      1. Reject p with err.
      2. Abort these steps.
  2. Resolve p with undefined.
3. Return p.

5.5.2

`has(cacheName)`

has(cacheName) method must run these steps or their equivalent:

Return a promise, p, resolved with the result of running the following substeps:
1. For each Record {[[key]], [[value]]} entry of its name to cache map, in key insertion order:
  1. If cacheName matches entry.[[key]], then:
    1. Return true.
2. Return false.

5.5.3

`open(cacheName)`

open(cacheName) method must run these steps or their equivalent:

Return a promise, p, resolved with the result of running the following substeps:
1. For each Record {[[key]], [[value]]} entry of its name to cache map, in key insertion order:
  1. If cacheName matches entry.[[key]], then:
    1. Return a new Cache object which is a copy of entry.[[value]].
    2. Abort these steps.
2. Let cache be a new Cache object.
3. Set a newly-created Record {[[key]]: cacheName, [[value]]: cache} to name to cache map.
4. Return cache.

5.5.4

`delete(cacheName)`

delete(cacheName) method must run these steps or their equivalent:

Let p be the result of running the algorithm specified in has(cacheName) method with cacheName as the argument.
Let q be transforming p with onFulfilled.
Upon fulfillment of p with value cacheExists, perform the following substeps, onFulfilled, in parallel:
1. If cacheExists is true, then:
  1. Delete a Record {[[key]], [[value]]} entry of its name to cache map where cacheName matches entry.[[key]].
  2. Resolve q with true.
  3. Abort these steps.
2. Else:
  1. Resolve q with flase.
Return q.

5.5.5

`keys()`

keys() method must run these steps or their equivalent:

The promise returned from this method resolves with the sequence of keys, cache names in DOMString, in insertion order.

Let resultArray be an empty array.
Return a promise, p, resolved with the result of running the following substeps:
1. For each Record {[[key]], [[value]]} entry of its name to cache map, in key insertion order:
  1. Add entry.[[key]] to resultArray.
2. Return resultArray.

Appendix A: Algorithms

The following definitions are the user agent's internal data structures used throughout the specification.

A scope to registration map is a List of the Record {[[key]], [[value]]} where [[key]] is a string that represents a scope url and [[value]] is a service worker registration.

An algorithm thread queue is a thread safe queue used to synchronize the set of concurrent entries of algorithm steps. The queue contains timestamps (with the assumptions), gained by algorithms, as its elements. The queue should satisfy the general properties of FIFO queue.

A registration queue is an algorithm thread queue for synchronizing the set of concurrent registration requests. The user agent must maintain a separate queue for each service worker registration keyed by its scope url. The queue is initially empty.

An installation queue is an algorithm thread queue for synchronizing the set of concurrent installation jobs. The user agent must maintain a separate queue for each service worker registration keyed by its scope url. The queue is initially empty.

An installation result handle queue is an algorithm thread queue for synchronizing the set of concurrent installation jobs. The user agent must maintain a separate queue for each service worker registration keyed by its scope url. The queue is initially empty.

9.1

Register

Input: client, a service worker client; scriptURL, an absolute URL; scopeURL, an absolute URL
Output: promise, a promise

If the result of running Is origin potentially trustworthy with the origin of scriptURL as the argument is Not Trusted, then:
1. Return a promise rejected with a "SecurityError" exception.
If the origin of scriptURL is not client's origin, then:
1. Return a promise rejected with a "SecurityError" exception.
If the origin of scopeURL is not client's origin, then:
1. Return a promise rejected with a "SecurityError" exception.
Run the following substeps atomically:
1. Let registration be the result of running the Get Registration algorithm passing scopeURL as the argument.
2. If registration is not null, then:
  1. Let newestWorker be the result of running the Get Newest Worker algorithm passing registration as the argument.
  2. If newestWorker is not null, scriptURL is equal to newestWorker's script url, and scriptURL is equal to registration's registering script url, then:
    1. If newestWorker is an active worker, then:
      1. If registration's uninstalling flag is set, unset it.
      2. Return a promise resolved with a ServiceWorkerRegistration object, setting its service worker client to client, which represents registration.
3. Else:
  1. Set registration to the result of running Set Registration algorithm passing scopeURL as its argument.
4. Set registration's registering script url to scriptURL.
5. Return the result of running the Update algorithm, or its equivalent, passing client and registration as the argument.

9.2

Update

The algorithm uses registration queue to synchronize the set of multiple registration requests. Implementers may use it or other synchronization primitives and methods to satisfy this requirement.

Input: client, a service worker client; registration, a service worker registration
Output: promise, a promise

Let p be a new promise.
Generate a timestamp and let timeStamp be the result value.
Push timeStamp to registration queue, installation queue, and installation result handle queue.
Run the following substeps in parallel:
1. CheckPriority: If the value of the top element of registration queue matches timeStamp, then:
  1. Pop the top element from registration queue.
2. Else:
  1. Wait until the top element of registration queue is popped.
  2. Jump to the step labeled CheckProirity.
  Wait is a blocking wait. Implementers may use a condition variable or its equivalent synchronization primitive.
3. Run the following substeps atomically:
  1. If registration's installing worker is not null, then:
    1. Terminate registration's installing worker.
    2. Run the Update State algorithm passing registration's installing worker and redundant as the arguments.
    3. Set registration's installing worker to null.
    4. The user agent may abort in-flight requests triggered by registration's installing worker.
  2. Let r be the associated request of the result of invoking the initial value of Request as constructor with registration's registering script url. If this throws an exception, then:
    1. Reject p with the exception.
    2. Pop the top element from installation queue and installation result handle queue.
    3. If the result of running Get Newest Worker algorithm passing registration as the argument is null, invoke Clear Registration algorithm passing registration as its argument.
    4. Abort these steps.
  3. Set r's context to serviceworker.
  4. Append `Service-Worker`/`script` to r's header list.
  5. Set r's skip service worker flag and r's synchronous flag.
  6. Let response be the result of running fetch using r, forcing a network fetch if cached entry is greater than 1 day old.
  7. If response is a network error, then:
    1. If r's redirect count is not zero, then:
      1. Reject p with a "SecurityError" exception.
      2. Pop the top element from installation queue and installation result handle queue.
      3. If the result of running Get Newest Worker algorithm passing registration as the argument is null, invoke Clear Registration algorithm passing registration as its argument.
      4. Abort these steps.
    2. Else:
      1. Reject p with a "NetworkError" exception.
      2. Pop the top element from installation queue and installation result handle queue.
      3. If the result of running Get Newest Worker algorithm passing registration as the argument is null, invoke Clear Registration algorithm passing registration as its argument.
      4. Abort these steps.
  8. Extract a MIME type from the response's header list. If this MIME type (ignoring parameters) is not one of text/javascript, application/x-javascript, and application/javascript, then:
    1. Reject p with a "SecurityError" exception.
    2. Pop the top element from installation queue and installation result handle queue.
    3. If the result of running Get Newest Worker algorithm passing registration as the argument is null, invoke Clear Registration algorithm passing registration as its argument.
    4. Abort these steps.
  9. Let serviceWorkerAllowed be the result of parsing `Service-Worker-Allowed` in response's header list.
  10. If serviceWorkerAllowed is failure, then:
    1. Reject p with a "SecurityError" exception.
    2. Pop the top element from installation queue and installation result handle queue.
    3. If the result of running Get Newest Worker algorithm passing registration as the argument is null, invoke Clear Registration algorithm passing registration as its argument.
    4. Abort these steps.
  11. Let scopeURL be registration's scope url.
  12. Let maxScopeString be null.
  13. If serviceWorkerAllowed is null, then:
    1. Set maxScopeString to "/" concatenated with the strings, except the last string that denotes the script's file name, in registration's registering script url's path (including empty strings), separated from each other by "/".
  14. Else:
    1. Let maxScope be the result of parsing serviceWorkerAllowed with registration's registering script url.
    2. Set maxScopeString to "/" concatenated with the strings in maxScope's path (including empty strings), separated from each other by "/".
  15. Let scopeString be "/" concatenated with the strings in scopeURL's path (including empty strings), separated from each other by "/".
  16. If scopeString starts with maxScopeString, do nothing.
  17. Else:
    1. Reject p with a "SecurityError" exception.
    2. Pop the top element from installation queue and installation result handle queue.
    3. If the result of running Get Newest Worker algorithm passing registration as the argument is null, invoke Clear Registration algorithm passing registration as its argument.
    4. Abort these steps.
  18. Let newestWorker be the result of running the Get Newest Worker algorithm passing registration as the argument.
  19. If newestWorker is not null, and newestWorker's script url is equal to registration's registering script url and response is a byte-for-byte match with the script of newestWorker, then:
    1. Resolve p with a ServiceWorkerRegistration object, setting its service worker client to client, which represents registration.
    2. Abort these steps.
  20. Else:
    1. Let worker be a new service worker for the script with registration's registering script url.
    2. If worker fails to start up, due to parse errors or uncaught errors, then:
      1. Reject p with the error.
      2. Pop the top element from installation queue and installation result handle queue.
      3. If the result of running Get Newest Worker algorithm is null, then:
        
        Invoke Clear Registration algorithm passing registration as its argument.
      4. Abort these steps.
4. Invoke Install algorithm, or its equivalent, with client, registration, worker, p, and timeStamp as its arguments.
Return p.

9.3

Soft Update

The user agent may call this as often as it likes to check for updates.

Input: registration, a service worker registration
Output: None

Let client be an empty environment settings object.
If registration's uninstalling flag is set, then:
1. Abort these steps.
If registration's installing worker is not null, then:
1. Abort these steps.
Invoke Update algorithm, or its equivalent, with client, registration as its argument.

Inspect whether the promise returned from Update algorithm should be returned to the caller (either UA internal context or reg.update()).

9.4

Install

The algorithm uses installation queue to synchronize the set of multiple installation jobs. Implementers may use it or other synchronization primitives and methods to satisfy this requirement.

Input: client, a service worker client; registration, a service worker registration; worker, a service worker; registrationPromise, a promise; timeStamp, a timestamp
Output: none

Let installFailed be false.
CheckPriority: If the value of the top element of installation queue matches timeStamp, then:
1. Pop the top element from installation queue.
Else:
1. Wait until the top element of installation queue is popped.
2. Jump to the step labeled CheckProirity.
Wait is a blocking wait. Implementers may use a condition variable or its equivalent synchronization primitive.
Run the following substeps atomically:
1. If registration's installing worker is not null, then:
  1. Terminate registration's installing worker.
  2. Run the Update State algorithm passing registration's installing worker and redundant as the arguments.
  3. The user agent may abort any in-flight requests triggered by registration's installing worker.
2. Set registration's installing worker to worker.
3. Run the Update State algorithm passing registration's installing worker and installing as the arguments.
4. Assert: registrationPromise is not null.
5. Resolve registrationPromise with a ServiceWorkerRegistration object, setting its service worker client to client, which represents registration.
6. Queue a task to fire a simple event named updatefound at all the ServiceWorkerRegistration objects that represent registration for all the service worker clients whose creation url matches registration's scope url.
7. Queue a task to run the following substeps:
  1. Let installingWorker be registration's installing worker.
  2. Run a worker, if not running, for a script with installingWorker's script url and installingWorker's environment settings object.
  3. Fire an event named install using InstallEvent interface at installingWorker's environment settings object's global object.
  4. Let event be null.
  5. For each event listener invoked:
    1. If any uncaught runtime script error occurs, then:
      1. Report the error for the script per the runtime script errors handling.
      2. Run the Update State algorithm passing registration's installing worker and redundant as the arguments.
      3. Set registration's installing worker to null.
      4. Pop the top element from installation result handle queue.
      5. If the result of running Get Newest Worker algorithm is null, then:
        
        Invoke Clear Registration algorithm passing registration as its argument.
      6. Abort these steps.
    2. Set event to the event for which this event listener was invoked.
  6. Let p be waiting for all of event's extend lifetime promises.
  7. Wait until p settles.
  8. If p rejected, then:
    1. Set installFailed to true.
  9. Else if p resolved with a value, then:
    1. Do nothing.
CheckResultHandlePriority: If the value of the top element of installation result handle queue matches timeStamp, then:
1. Pop the top element from installation result handle queue.
Else:
1. Wait until the top element of installation result handle queue is popped.
2. Jump to the step labeled CheckResultHandlePriority.
Wait is a blocking wait. Implementers may use a condition variable or its equivalent synchronization primitive.
Run the following substeps atomically:
1. Wait for the task queued by the step 4.7 to have executed.
2. If registration's installing worker is null, then:
  1. Abort these steps.
3. If installFailed is true, then:
  1. Run the Update State algorithm passing registration's installing worker and redundant as the arguments.
  2. Set registration's installing worker to null.
  3. If the result of running Get Newest Worker algorithm is null, then:
    1. Invoke Clear Registration algorithm passing registration as its argument.
  4. Abort these steps.
4. If registration's waiting worker is not null, then:
  1. Terminate registration's waiting worker.
  2. Run the Update State algorithm passing registration's waiting worker and redundant as the arguments.
  3. The user agent may abort in-flight requests triggered by registration's waiting worker.
5. Set registration's waiting worker to registration's installing worker.
6. Set registration's installing worker to null.
7. Run the Update State algorithm passing registration's waiting worker and installed as the arguments.
8. If registration's uninstalling flag is set before timeStamp, then:
  1. Wait until a Record {[[key]], [[value]]} entry of its scope to registration map where registration's scope url matches entry.[[key]] is deleted.
  2. Set a newly-created Record {[[key]]: registration's scope url, [[value]]: registration} to scope to registration map.
  3. Unset registration's uninstalling flag.
9. If registration's waiting worker's skip waiting flag is set, then:
  1. For each service worker client serviceWorkerClient whose creation url matches registration's scope url:
    1. Let exitingWorker be the active worker that controls serviceWorkerClient.
    2. If exitingWorker is not null, then:
      1. Wait for exitingWorker to finish handling any in-progress requests.
      2. Terminate exitingWorker.
      3. Run the Update State algorithm passing exitingWorker and redundant as the arguments.
  2. Run Activate algorithm, or its equivalent, passing registration as the argument.
  3. Abort these steps.
Wait until no service worker client is using registration or registration's waiting worker's skip waiting flag is set.
If registration's waiting worker waitingWorker is not null and waitingWorker's skip waiting flag is not set, invoke Activate algorithm, or its equivalent, with registration as its argument.

9.5

Activate

Input: registration, a service worker registration
Output: None

Run the following substeps atomically:
1. Let activateFailed be false.
2. Let activatingWorker be registration's waiting worker.
3. Let exitingWorker be registration's active worker.
4. If activatingWorker is null, then:
  1. Abort these steps.
5. If exitingWorker is not null, then:
  1. Wait for exitingWorker to finish handling any in-progress requests.
  2. Terminate exitingWorker.
  3. Run the Update State algorithm passing exitingWorker and redundant as the arguments.
6. Set registration's active worker to activatingWorker.
7. Set registration's waiting worker to null.
8. Run the Update State algorithm passing registration's active worker and activating as the arguments.
9. For each service worker client client whose creation url matches registration's scope url:
  1. If client is a window client, then:
    1. Unassociate client's responsible document from its application cache, if it has one.
  2. Else if client is a shared worker client, then:
    1. Unassociate client's global object from its application cache, if it has one.
  Resources will now use the service worker registration instead of the existing application cache.
10. Queue a task to fire a simple event named controllerchange at all the ServiceWorkerContainer objects for all the service worker clients which use registration.
11. Queue a task to run the following substeps:
  1. Let activeWorker be registration's active worker.
  2. Run a worker, if not running, for a script with activeWorker's script url and activeWorker's environment settings object.
  3. Fire an event named activate using ExtendableEvent interface at activeWorker's environment settings object's global object.
  4. Let event be null.
  5. For each event listener invoked:
    1. If any uncaught runtime script error occurs, then:
      1. Report the error for the script per the runtime script errors handling.
      2. Run the Update State algorithm passing registration's active worker and redundant as the arguments.
      3. Set registration's active worker to null.
      4. Abort these steps.
    2. Set event to the event for which this event listener was invoked.
  6. Let p be waiting for all of event's extend lifetime promises.
  7. Wait until p settles.
  8. If p rejected, then:
    1. Set activateFailed to true.
  9. Else if p resolved with a value, then:
    1. Do nothing.
12. Wait for the task queued by the previous step to have executed.
13. If activateFailed is true, then:
  1. Run the Update State algorithm passing registration's active worker and redundant as the arguments.
  2. Set registration's active worker to null.
  3. Abort these steps.
14. Run the Update State algorithm passing registration's active worker and activated as the arguments.

9.6

Handle Fetch

The Handle Fetch algorithm is the entry point for the fetch handling handed to the service worker context.

Input: request, a request
Output: response, a response

Let handleFetchFailed be false.
Let respondWithEntered be false.
Let eventCanceled be false.
Let r be a new Request object associated with request.
Let headersObject be r's headers attribute value.
Set headersObject's guard to immutable.
Let response be null.
Let registration be null.
Let client be request's client.
Assert: request's context is not serviceworker.
If request is a potential client request, then:
1. Return null.
Else if request is a client request, then:
1. If the navigation triggering request was initiated with a shift+reload or equivalent, then:
  1. Return null.
2. Set registration to the result of running Match Service Worker Registration algorithm, or its equivalent, passing r's url attribute value as the argument.
3. If registration is null or registration's active worker is null, return null.
4. Set client's active worker to registration's active worker.
From this point, the service worker client starts to use its active worker's containing service worker registration.
Else if request is a resource request, then:
1. If client's active worker in non-null, then:
  1. Set registration to client's active worker's containing service worker registration.
2. Else:
  1. Return null.
Let matchedWorker be registration's active worker.
If matchedWorker's state is activating, then:
1. Wait for matchedWorker's state to become activated.
2. If matchedWorker's activation fails, then:
  1. Return null.
Queue a task to run the following substeps:
1. Let activeWorker be registration's active worker.
2. Run a worker, if not running, for a script with activeWorker's script url and activeWorker's environment settings object.
3. Fire an event named fetch, using FetchEvent interface, with request attribute initialized to r, client attribute initialized to client of the request, in the form of Client object, and isReload initialized to true if event was dispatched with the user's intention for the page reload, and false otherwise, at activeWorker's environment settings object's global object.
4. For each event listener invoked:
  1. If any uncaught runtime script error occurs, then:
    1. Report the error for the script per the runtime script errors handling.
    2. Abort these steps.
  2. Let event be the event for which this event listener was invoked.
  3. If event's respond-with entered flag is set, then:
    1. Set respondWithEntered to true.
  4. If event's wait to respond flag is set, then:
    1. Wait until event's wait to respond flag is unset.
    2. If event's respond-with error flag is set, then:
      1. Set handleFetchFailed to true.
    3. Else:
      1. If the argument passed into the event's respondWith(r) method arg is a Response object, then:
        Set response to arg.
      2. Else:
        
        Set response to the value which arg resolved with.
  5. If event's canceled flag is set, then:
    1. Set eventCanceled to true.
Wait for the task queued by the previous step to have executed.
If respondWithEntered is false, then:
1. If eventCanceled is true, then:
  1. Return a network error and run the following substeps in parallel.
2. Else:
  1. Return null and run the following substeps in parallel.
3. If request is a client request, then:
  1. Invoke Soft Update algorithm, or its equivalent, with registration.
4. Abort these steps.
If handleFetchFailed is true, then:
1. Return a network error and run the following substeps in parallel.
2. If request is a client request, then:
  1. Invoke Soft Update algorithm, or its equivalent, with registration.
Else:
1. Return a response represented by response and run the following substeps in parallel.
2. If request is a client request, then:
  1. Invoke Soft Update algorithm, or its equivalent, with registration.

9.7

Handle Functional Event

Input: registration, a service worker registration; callbackSteps, an algorithm
Output: None

Queue a task to run Handle Functional Event On Scheduled Task algorithm, or its equivalent, with registration and callbackSteps.

Event loop and task queuing model for this algorithm will be specified.

9.8

Handle Functional Event On Scheduled Task

Input: registration, a service worker registration; callbackSteps, an algorithm
Output: None

Assert: a Record with the [[value]] equals to registration is contained in scope to registration map.
Assert: registration's active worker is not null.
Let activeWorker be registration's active worker.
Run a worker, if not running, for a script with activeWorker's script url and activeWorker's environment settings object.
Invoke callbackSteps, defined by the caller of the algorithm which queued this task, with activeWorker's environment settings object's global object as its argument.
Return.

9.9

Handle Service Worker Client Unload

The user agent must run these steps, or their equivalent, when a service worker client unloads by unloading, being killed, or terminating.

Input: client, a service worker client
Output: None

Run the following steps atomically.
Let registration be the service worker registration used by client.
If registration is null, then:
1. Abort these steps.
If any other service worker client is using registration, then:
1. Abort these steps.
If registration's uninstalling flag is true, then:
1. Invoke Clear Registration algorithm passing registration as its argument.
2. Abort these steps.
If registration.waiting is not null:
1. Run Activate algorithm, or its equivalent, with registration at the argument.

9.10

Unregister

Input: client, a service worker client; scope, an absolute URL
Output: promise, a promise

Let promise be a new promise.
Run the following substeps in parallel:
1. If the origin of scope is not client's origin, then:
  1. Reject promise with a "SecurityError" exception.
  2. Abort these steps.
2. Let registration be the result of running Get Registration algorithm passing scope as the argument.
3. If registration is null, then:
  1. Resolve promise with false.
  2. Abort these steps.
4. Set registration's uninstalling flag.
5. Resolve promise with true.
6. If no service worker client is using registration, then:
  1. If registration's uninstalling flag is unset, then:
    1. Abort these steps.
  2. Invoke Clear Registration algorithm passing registration as its argument.
Return promise.

9.11

Set Registration

Input: scope, an absolute URL
Output: registration, a service worker registration

Run the following steps atomically.
Let scopeString be serialized scope with the exclude fragment flag set.
Let registration be a new service worker registration whose scope url is set to scope.
Set a newly-created Record {[[key]]: scopeString, [[value]]: registration} to scope to registration map.
Return registration.

9.12

Clear Registration

Input: registration, a service worker registration
Output: None

Run the following steps atomically.
If registration's installing worker is not null, then:
1. Terminate registration's installing worker.
2. Run the Update State algorithm passing registration's installing worker and redundant as the arguments.
3. Set registration's installing worker to null.
4. The user agent may abort in-flight requests triggered by registration's installing worker.
If registration's waiting worker is not null, then:
1. Terminate registration's waiting worker.
2. Run the Update State algorithm passing registration's waiting worker and redundant as the arguments.
3. Set registration's waiting worker to null.
4. The user agent may abort in-flight requests triggered by registration's waiting worker.
If registration's active worker is not null, then:
1. Terminate registration's active worker.
2. Run the Update State algorithm passing registration's active worker and redundant as the arguments.
3. Set registration's active worker to null.
4. The user agent may abort in-flight requests triggered by registration's active worker.
Delete a Record {[[key]], [[value]]} entry of its scope to registration map where registration's scope url matches entry.[[key]].

9.13

Update State

Input: worker, a service worker; state, a service worker's state
Output: None

Set worker's state to state.
Let serviceWorkers be an array containing all the ServiceWorker objects associated with worker for all the browsing contexts' Document objects and the ServiceWorkerGlobalScope object represented by worker.
For each serviceWorker in serviceWorkers:
1. Queue a task to fire a simple event named statechange at serviceWorker.

9.14

Match Service Worker Registration

Input: clientURL, an absolute URL
Output: registration, a service worker registration

Run the following steps atomically.
Let clientURLString be serialized clientURL.
Let matchingScope be the longest [[key]] in scope to registration map starting with the value of clientURLString.
Let matchingScopeURL be the result of parsing matchingScope.
Let registration be the result of running Get Registration algorithm passing matchingScopeURL as the argument.
If registration is not null and registration's uninstalling flag is set, then:
1. Return null.
Return registration.

9.15

Get Registration

Input: scope, an absolute URL
Output: registration, a service worker registration

Run the following steps atomically.
Let registration be null.
Let scopeString be serialized scope with the exclude fragment flag set.
For each Record {[[key]], [[value]]} entry of its scope to registration map:
1. If scopeString matches entry.[[key]], then:
  1. Set registration to entry.[[value]].
Return registration.

9.16

Get Newest Worker

Input: registration, a service worker registration
Output: worker, a service worker

Run the following steps atomically.
Let newestWorker be null.
If registration's installing worker is not null, then:
1. Set newestWorker to registration's installing worker.
Else if registration's waiting worker is not null, then:
1. Set newestWorker to registration's waiting worker.
Else if registration's active worker is not null, then:
1. Set newestWorker to registration's active worker.
Return newestWorker.

9.17

Capture Window Client

Input: browsingContext, a browsing context
Output: windowClient, a WindowClient object

Let windowClient be a new WindowClient object representing browsingContext.
Set windowClient's visibility state to browsingContext's active document's visibilityState attribute value.
Set windowClient's focus state to the result of running browsingContext's active document's hasFocus() method.
Return windowClient.

9.18

Query Cache

Input: request, a Request object; options, a CacheQueryOptions object, optional; targetStorage, an array that has [Request, Response] pairs as its elements, optional
Output: resultArray, an array that has [Request, Response] pairs as its elements

Let requestArray be an empty array.
Let responseArray be an empty array.
Let resultArray be an empty array.
If options.ignoreMethod is false and request.method is neither "GET" nor "HEAD", then:
1. Return resultArray.
Let cachedURL and requestURL be null.
Let serializedCachedURL and serializedRequestURL be null.
If the optional argument targetStorage is omitted, then:
1. For each fetching record entry of its request to response map, in key insertion order:
  1. Set cachedURL to entry.[[key]]'s associated request's url.
  2. Set requestURL to request's associated request's url.
  3. If options.ignoreSearch is true, then:
    1. Set cachedURL's query to the empty string.
    2. Set requestURL's query to the empty string.
  4. Set serializedCachedURL to serialized cachedURL.
  5. Set serializedRequestURL to serialized requestURL.
  6. If options.prefixMatch is true, then:
    1. Set serializedCachedURL to the substring of itself from the start, with the length of serializedRequestURL.
  7. If serializedCachedURL matches serializedRequestURL, then:
    1. Add entry.[[key]] to requestArray.
    2. Add entry.[[value]] to responseArray.
Else:
1. For each record in targetStorage:
  1. Set cachedURL to record[0]'s associated request's url.
  2. Set requestURL to request's associated request's url.
  3. If options.ignoreSearch is true, then:
    1. Set cachedURL's query to the empty string.
    2. Set requestURL's query to the empty string.
  4. Set serializedCachedURL to serialized cachedURL.
  5. Set serializedRequestURL to serialized requestURL.
  6. If options.prefixMatch is true, then:
    1. Set serializedCachedURL to the substring of itself from the start, with the length of serializedRequestURL.
  7. If serializedCachedURL matches serializedRequestURL, then:
    1. Add record[0] to requestArray.
    2. Add record[1] to responseArray.
For each cachedResponse in responseArray with the index index:
1. Let cachedRequest be the indexth element in requestArray.
2. If the result of running cachedResponse.headers object's has(name) method with "Vary" as the argument is false, or options.ignoreVary is true, then:
  1. Add an array [cachedRequest, cachedResponse] to resultArray.
  2. Continue to the next iteration of the loop.
3. Let varyHeaders be the array containing the elements corresponding to the field-values of the Vary header.
4. Let matchFailed be false.
5. For each f in varyHeaders:
  1. If f matches "*", then:
    1. Continue to the next iteration of the loop.
  2. If the result of running cachedRequest.headers object's get(name) method with f as the argument does not match the result of running request.headers object's get(name) method with f as the argument, then:
    1. Set matchFailed to true.
    2. Break the loop.
6. If matchFailed is false, then:
  1. Add an array [cachedRequest, cachedResponse] to resultArray.
Return resultArray.

9.19

Batch Cache Operations

Input: operations, an array of CacheBatchOperation dictionary objects
Output: q, a promise resolves with an array of Response objects.

Let p be a promise resolved with no value.
Let q be transforming p with onFulfilled.
Upon fulfillment of p with value v, perform the following substeps, onFulfilled, in parallel:
1. Let itemsCopy be a new request to response map that is a copy of its context object's request to response map.
2. Let addedRecords be an empty array.
3. Try running the following substeps atomically:
  1. Let resultArray be an empty array.
  2. For each operation in operations with the index index:
    1. If operation.type matches neither "delete" nor "put", then:
      1. Throw a TypeError.
    2. If operation.type matches "delete" and operation.response is not null, then:
      1. Throw a TypeError.
    3. If the result of running Query Cache algorithm passing operation.request, operation.options, and addedRecords as the arguments is not an empty array, then:
      1. Throw an "InvalidStateError" exception.
    4. Let requestResponseArray be the result of running Query Cache algorithm passing operation.request and operation.options as the arguments.
    5. For each requestResponse in requestResponseArray:
      1. If operation.type matches "delete", remove the corresponding fetching record from request to response map.
    6. If operation.type matches "put", then:
      1. If operation.response is null, then:
        
        Throw a TypeError.
      2. Let r be operation.request's associated request.
      3. If r's url's scheme is not one of "http" and "https", then:
        
        Throw a TypeError.
      4. If r's method is not `GET`, then:
        
        Throw a TypeError.
      5. If operation.options is not null, then:
        
        Throw a TypeError.
      6. If there exists a corresponding fetching record fetchingRecord for operation.request and operation.response in request to response map, set fetchingRecord.[[value]] to operation.response.
      7. Else, set a newly-created fetching record {[[key]]: operation.request, [[value]]: operation.response} to request to response map.
        The cache commit is allowed as long as the response's headers are available.
      8. Add an array [operation.request, operation.response] to addedRecords.
    7. Add operation.response to resultArray.
  3. Resolve q with resultArray.
4. And then, if an exception was thrown, then:
  1. Set the context object's request to response map to itemsCopy.
  2. Reject q with the exception
Return q.

Service Workers

W3C Working Draft 5 February 2015

Abstract

Status of This Document