MDN will be in maintenance mode on Friday September 22nd, starting at 10 AM Pacific / 5 PM UTC, for about 1 hour.

The Fetch API provides an interface for fetching resources (including across the network). It will seem familiar to anyone who has used XMLHttpRequest, but the new API provides a more powerful and flexible feature set.

Concepts and usage

Fetch provides a generic definition of Request and Response objects (and other things involved with network requests). This will allow them to be used wherever they are needed in the future, whether it’s for service workers, Cache API and other similar things that handle or modify requests and responses, or any kind of use case that might require you to generate your own responses programmatically.

It also provides a definition for related concepts such as CORS and the HTTP origin header semantics, supplanting their separate definitions elsewhere.

For making a request and fetching a resource, use the GlobalFetch.fetch method. It is implemented in multiple interfaces, specifically Window and WorkerGlobalScope. This makes it available in pretty much any context you might want to fetch resources in.

The fetch() method takes one mandatory argument, the path to the resource you want to fetch. It returns a promise that resolves to the Response to that request, whether it is successful or not. You can also optionally pass in an init options object as the second argument (see Request).

Once a Response is retrieved, there are a number of methods available to define what the body content is and how it should be handled (see Body).

You can create a request and response directly using the Request() and Response() constructors, but you are unlikely to do this directly. Instead, these are more likely to be created as results of other API actions (for example, FetchEvent.respondWith from service workers).

Note: Find out more about using the Fetch API features in Using Fetch, and study concepts in Fetch basic concepts.

Fetch Interfaces

GlobalFetch
Contains the fetch() method used to fetch a resource.
Headers
Represents response/request headers, allowing you to query them and take different actions depending on the results.
Request
Represents a resource request.
Response
Represents the response to a request.

Experimental fetch controller/signal/observer interfaces

Also known as “cancellable fetch”, the following interfaces contain functionality to allow fetch request operations to be observed and controlled during their lifetimes.

FetchController
Represents a controller object that allows you to control one or more fetch requests.
FetchSignal
Represents a signal object that allows you to communicate with a fetch request and control it via a FetchController.
FetchObserver
Represents an observer object that allows you to retrieve information concerning the status of a fetch request.
ObserverCallback
Provides a callback function that runs when the fetch request it is assocated with runs. This provides a FetchObserver object that can be used to retrieve information concerning the status of a fetch request.

Fetch mixin

Body
Provides methods relating to the body of the response/request, allowing you to declare what its content type is and how it should be handled.

Specifications

Specification Status Comment
Fetch Living Standard Initial definition

Browser compatibility

Feature Chrome Edge Firefox (Gecko) IE Opera Safari (WebKit)
Basic support 42 14 39 (39)
34[1]
52 (52)[2]
No support 29
28[1]
10.1
Streaming response body 43 14 ? No support ? No support
Experimental controller/signal/observer No support No support No support[3] No support No support No support
Feature Android Webview Chrome for Android Edge Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support 42 42 (Yes) (Yes) No support No support 10.1
Streaming response body 43 43 (Yes) (Yes) No support ? No support
Experimental controller/signal/observer No support No support No support No support[3] No support No support No support

[1] This API is implemented behind a preference.

[2] Prior to Firefox 52, get() only returned the first value in the specified header, with getAll() returning all values. From 52 onwards, get() now returns all values and getAll() has been removed.

[3] Hidden behind a preference in 55+ Nightly. In about:config, you need to create two new boolean prefs — dom.fetchObserver.enabled and dom.fetchController.enabled — and set the values of both to true.

See also