The fetch()
method of the WindowOrWorkerGlobalScope
mixin starts the process of fetching a resource from the network, returning a promise which is fulfilled once the response is available. The promise resolves to the Response
object representing the response to your request. The promise does not reject on HTTP errors — it only rejects on network errors. You must use then
handlers to check for HTTP errors.
WindowOrWorkerGlobalScope
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 only rejects when a network error is encountered (which is usually when thereβs a permissions issue or similar). A fetch()
promise does not reject on HTTP errors (404
, etc.). Instead, a then()
handler must check the Response.ok
and/or Response.status
properties.
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
const fetchResponsePromise = fetch(resource [, init])
Parameters
resource
- This defines the resource that you wish to fetch. This can either be:
init
Optional-
An 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
. Note that theOrigin
header is not set on Fetch requests with a method ofHEAD
orGET
.
(This behavior was corrected in Firefox 65 — see bug 1508661). headers
- Any headers you want to add to your request, contained within a
Headers
object or an object literal withByteString
values. Note that some names are forbidden. body
- Any body that you want to add to your request: this can be a
Blob
,BufferSource
,FormData
,URLSearchParams
,USVString
, orReadableStream
object. Note that a request using theGET
orHEAD
method cannot have a body. mode
- The mode you want to use for the request, e.g.,
cors
,no-cors
, orsame-origin
. credentials
- The request credentials you want to use for the request:
omit
,same-origin
, orinclude
. To automatically send cookies for the current domain, this option must be provided. Starting with Chrome 50, this property also takes aFederatedCredential
instance or aPasswordCredential
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), ormanual
(handle redirects manually). In Chrome the default isfollow
(before Chrome 47 it defaulted tomanual
). referrer
- A
USVString
specifying the referrer of the request. This can be a same-origin URL,about:client
, or an empty string. referrerPolicy
- Specifies the referrer policy to use for the request. May be one of
no-referrer
,no-referrer-when-downgrade
,same-origin
,origin
,strict-origin
,origin-when-cross-origin
,strict-origin-when-cross-origin
, orunsafe-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 thekeepalive
flag is a replacement for theNavigator.sendBeacon()
API. signal
- An
AbortSignal
object instance; allows you to communicate with a fetch request and abort it if desired via anAbortController
.
Return value
A Promise
that resolves to a Response
object.
Exceptions
AbortError
- The request was aborted due to a call to the
AbortController
methodabort()
method. TypeError
- The specified URL string includes user credentials. This information should instead be provided using an
Authorization
header.
Examples
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.
const myImage = document.querySelector('img'); let myRequest = new Request('flowers.jpg'); fetch(myRequest) .then(function(response) { if (!response.ok) { throw new Error(`HTTP error! status: ${response.status}`); } return response.blob(); }) .then(function(response) { let objectURL = URL.createObjectURL(response); myImage.src = objectURL; });
In the 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()
:
const myImage = document.querySelector('img'); let myHeaders = new Headers(); myHeaders.append('Content-Type', 'image/jpeg'); const myInit = { method: 'GET', headers: myHeaders, mode: 'cors', cache: 'default' }; let myRequest = new Request('flowers.jpg'); fetch(myRequest, myInit).then(function(response) { // ... });
You could also pass the init
object in with the Request
constructor to get the same effect:
let myRequest = new Request('flowers.jpg', myInit);
You can also use an object literal as headers
in init
.
const myInit = { method: 'GET', headers: { 'Content-Type': 'image/jpeg' }, mode: 'cors', cache: 'default' }; let 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
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
fetch | Chrome Full support 42 | Edge Full support 14 | Firefox
Full support
39
| IE No support No | Opera
Full support
29
| Safari Full support 10.1 | WebView Android Full support 42 | Chrome Android Full support 42 | Firefox Android
Full support
39
| Opera Android
Full support
29
| Safari iOS Full support 10.3 | Samsung Internet Android Full support 4.0 |
Support for blob: and data: | Chrome Full support 48 | Edge Full support 79 | Firefox ? | IE No support No | Opera ? | Safari ? | WebView Android Full support 43 | Chrome Android Full support 48 | Firefox Android ? | Opera Android ? | Safari iOS ? | Samsung Internet Android Full support 5.0 |
referrerPolicy | Chrome Full support 52 | Edge Full support 79 | Firefox Full support 52 | IE No support No | Opera Full support 39 | Safari Full support 11.1 | WebView Android Full support 52 | Chrome Android Full support 52 | Firefox Android Full support 52 | Opera Android Full support 41 | Safari iOS No support No | Samsung Internet Android Full support 6.0 |
signal | Chrome Full support 66 | Edge Full support 16 | Firefox Full support 57 | IE No support No | Opera Full support 53 | Safari Full support 11.1 | WebView Android Full support 66 | Chrome Android Full support 66 | Firefox Android Full support 57 | Opera Android Full support 47 | Safari iOS Full support 11.3 | Samsung Internet Android Full support 9.0 |
Streaming response body | Chrome Full support 43 | Edge Full support 14 | Firefox
Full support
Yes
| IE No support No | Opera Full support 29 | Safari Full support 10.1 | WebView Android Full support 43 | Chrome Android Full support 43 | Firefox Android No support No | Opera Android No support No | Safari iOS Full support 10.3 | Samsung Internet Android Full support 4.0 |
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.