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The fetch() method of the WindowOrWorkerGlobalScope mixin starts the process of fetching a resource from the network. This returns a promise that resolves to the Response object representing the response to your request.

WorkerOrGlobalScope is implemented by both Window and WorkerGlobalScope, which means that the fetch() method is available in pretty much any context in which you might want to fetch resources.

A fetch() promise rejects with a TypeError when a network error is encountered, although this usually means a permissions issue or similar. An accurate check for a successful fetch() would include checking that the promise resolved, then checking that the Response.ok property has a value of true. An HTTP status of 404 does not constitute a network error.

The fetch() method is controlled by the connect-src directive of Content Security Policy rather than the directive of the resources it's retrieving.

Note: The fetch() method's parameters are identical to those of the Request() constructor.

Syntax

Promise<Response> fetch(input[, init]);

Parameters

input
This defines the resource that you wish to fetch. This can either be:
  • A USVString containing the direct URL of the resource you want to fetch. Some browsers accept blob: and data: as schemes.
  • A Request object.
init Optional
An options object containing any custom settings that you want to apply to the request. The possible options are:
  • method: The request method, e.g., GET, POST.
  • headers: Any headers you want to add to your request, contained within a Headers object or an object literal with ByteString values.
  • body: Any body that you want to add to your request: this can be a Blob, BufferSource, FormData, URLSearchParams, or USVString object. Note that a request using the GET or HEAD method cannot have a body.
  • mode: The mode you want to use for the request, e.g., cors, no-cors, or same-origin.
  • credentials: The request credentials you want to use for the request: omit, same-origin, or include. To automatically send cookies for the current domain, this option must be provided. Starting with Chrome 50, this property also takes a FederatedCredential instance or a PasswordCredential instance.
  • cache: The cache mode you want to use for the request.
  • redirect: The redirect mode to use: follow (automatically follow redirects), error (abort with an error if a redirect occurs), or manual (handle redirects manually). In Chrome the default is follow (before Chrome 47 it defaulted to manual).
  • referrer: A USVString specifying no-referrerclient, or a URL. The default is client.
  • referrerPolicy: Specifies the value of the referer HTTP header. May be one of no-referrer, no-referrer-when-downgrade, origin, origin-when-cross-origin, unsafe-url.
  • integrity: Contains the subresource integrity value of the request (e.g., sha256-BpfBw7ivV8q2jLiT13fxDYAe2tJllusRSZ273h2nFSE=).
  • keepalive: The keepalive option can be used to allow the request to outlive the page. Fetch with the keepalive flag is a replacement for the Navigator.sendBeacon() API. 
  • signal: An AbortSignal object instance; allows you to communicate with a fetch request and abort it if desired via an AbortController.

Return value

A Promise that resolves to a Response object.

Exceptions

Type Description
AbortError The request was aborted (using AbortController.abort()).
TypeError Since Firefox 43, fetch() will throw a TypeError if the URL has credentials, such as http://user:password@example.com.

Example

In our Fetch Request example (see Fetch Request live) we create a new Request object using the relevant constructor, then fetch it using a fetch() call. Since we are fetching an image, we run Body.blob() on the response to give it the proper MIME type so it will be handled properly, then create an Object URL of it and display it in an <img> element.

var myImage = document.querySelector('img');

var myRequest = new Request('flowers.jpg');

fetch(myRequest).then(function(response) {
  return response.blob();
}).then(function(response) {
  var objectURL = URL.createObjectURL(response);
  myImage.src = objectURL;
});

In our Fetch with init then Request example (see Fetch Request init live) we do the same thing except that we pass in an init object when we invoke fetch():

var myImage = document.querySelector('img');

var myHeaders = new Headers();
myHeaders.append('Content-Type', 'image/jpeg');

var myInit = { method: 'GET',
               headers: myHeaders,
               mode: 'cors',
               cache: 'default' };

var myRequest = new Request('flowers.jpg');

fetch(myRequest,myInit).then(function(response) {
  ... 
});

Note that you could also pass the init object in with the Request constructor to get the same effect, e.g.:

var myRequest = new Request('flowers.jpg', myInit);

You can also use an object literal as headers in init.

var myInit = { method: 'GET',
               headers: {
                   'Content-Type': 'image/jpeg'
               },
               mode: 'cors',
               cache: 'default' };

var myRequest = new Request('flowers.jpg', myInit);

Specifications

Specification Status Comment
Fetch
The definition of 'fetch()' in that specification.
Living Standard Defined in a WindowOrWorkerGlobalScope partial in the newest spec.
Fetch
The definition of 'fetch()' in that specification.
Living Standard Initial definition
Credential Management Level 1 Working Draft Adds FederatedCredential or PasswordCredential instance as a possible value for init.credentials.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome Full support 42Edge Full support 14Firefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enable preference. To change preferences in Firefox, visit about:config.
Full support 52
Notes
Notes fetch() now defined on WindowOrWorkerGlobalScope mixin.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari Full support 10WebView Android Full support 42Chrome Android Full support 42Edge Mobile Full support 14Firefox Android Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enable preference. To change preferences in Firefox, visit about:config.
Full support 52
Notes
Notes fetch() now defined on WindowOrWorkerGlobalScope mixin.
Opera Android ? Safari iOS Full support 10Samsung Internet Android ?
Streaming response body
Experimental
Chrome Full support 43Edge Full support 14Firefox Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the dom.streams.enabled preference and the javascript.options.streams preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29Safari Full support 10WebView Android Full support 43Chrome Android Full support 43Edge Mobile Full support 14Firefox Android No support NoOpera Android No support NoSafari iOS Full support 10Samsung Internet Android ?
Support for blob: and data:
Experimental
Chrome Full support 48Edge No support NoFirefox ? IE No support NoOpera ? Safari ? WebView Android Full support 43Chrome Android Full support 43Edge Mobile No support NoFirefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?
referrerPolicyChrome Full support 52Edge No support NoFirefox Full support 52IE No support NoOpera Full support 39Safari Full support 11.1WebView Android Full support 52Chrome Android Full support 52Edge Mobile No support NoFirefox Android Full support 52Opera Android Full support 39Safari iOS No support NoSamsung Internet Android ?
signal
Experimental
Chrome ? Edge ? Firefox Full support 57IE No support NoOpera ? Safari No support NoWebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 57Opera Android ? Safari iOS No support NoSamsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also