Use XMLHttpRequest (XHR) objects to interact with servers. You can retrieve data from a URL without having to do a full page refresh. This enables a Web page to update just part of a page without disrupting what the user is doing. XMLHttpRequest is used heavily in Ajax programming.

Despite its name, XMLHttpRequest can be used to retrieve any type of data, not just XML, and it supports protocols other than HTTP (including file and ftp).

If your communication needs involve receiving event or message data from the server, consider using server-sent events through the EventSource interface. For full-duplex communication, WebSockets may be a better choice.

Constructor

XMLHttpRequest()
The constructor initializes an XMLHttpRequest. It must be called before any other method calls.

Properties

This interface also inherits properties of XMLHttpRequestEventTarget and of EventTarget.

XMLHttpRequest.onreadystatechange
An EventHandler that is called whenever the readyState attribute changes.
XMLHttpRequest.readyState Read only
Returns an unsigned short, the state of the request.
XMLHttpRequest.response Read only
Returns an ArrayBuffer, Blob, Document, JavaScript object, or a DOMString, depending on the value of XMLHttpRequest.responseType. that contains the response entity body.
XMLHttpRequest.responseText Read only
Returns a DOMString that contains the response to the request as text, or null if the request was unsuccessful or has not yet been sent.
XMLHttpRequest.responseType
Is an enumerated value that defines the response type.
XMLHttpRequest.responseURL Read only
Returns the serialized URL of the response or the empty string if the URL is null.
XMLHttpRequest.responseXML Read only Not available to workers
Returns a Document containing the response to the request, or null if the request was unsuccessful, has not yet been sent, or cannot be parsed as XML or HTML.
XMLHttpRequest.status Read only
Returns an unsigned short with the status of the response of the request.
XMLHttpRequest.statusText Read only
Returns a DOMString containing the response string returned by the HTTP server. Unlike XMLHTTPRequest.status, this includes the entire text of the response message ("200 OK", for example).

Note: The HTTP/2 specification (8.1.2.4 Response Pseudo-Header Fields), HTTP/2 does not define a way to carry the version or reason phrase that is included in an HTTP/1.1 status line.

XMLHttpRequest.timeout
Is an unsigned long representing the number of milliseconds a request can take before automatically being terminated.
XMLHttpRequestEventTarget.ontimeout
Is an EventHandler that is called whenever the request times out.
XMLHttpRequest.upload Read only
Is an XMLHttpRequestUpload, representing the upload process.
XMLHttpRequest.withCredentials
Is a Boolean that indicates whether or not cross-site Access-Control requests should be made using credentials such as cookies or authorization headers.

Non-standard properties

XMLHttpRequest.channelRead only
Is a nsIChannel. The channel used by the object when performing the request.
XMLHttpRequest.mozAnonRead only
Is a boolean. If true, the request will be sent without cookie and authentication headers.
XMLHttpRequest.mozSystemRead only
Is a boolean. If true, the same origin policy will not be enforced on the request.
XMLHttpRequest.mozBackgroundRequest
Is a boolean. It indicates whether or not the object represents a background service request.
XMLHttpRequest.mozResponseArrayBuffer Obsolete since Gecko 6 Read only
Is an ArrayBuffer. The response to the request, as a JavaScript typed array.
XMLHttpRequest.multipartObsolete since Gecko 22
This Gecko-only feature, a boolean, was removed in Firefox/Gecko 22. Please use Server-Sent Events, Web Sockets, or responseText from progress events instead.

Event handlers

onreadystatechange as a property of the XMLHttpRequest instance is supported in all browsers.

Since then, a number of additional event handlers have been implemented in various browsers (onload, onerror, onprogress, etc.). See Using XMLHttpRequest.

More recent browsers, including Firefox, also support listening to the XMLHttpRequest events via standard addEventListener() APIs in addition to setting on* properties to a handler function.

Methods

XMLHttpRequest.abort()
Aborts the request if it has already been sent.
XMLHttpRequest.getAllResponseHeaders()
Returns all the response headers, separated by CRLF, as a string, or null if no response has been received.
XMLHttpRequest.getResponseHeader()
Returns the string containing the text of the specified header, or null if either the response has not yet been received or the header doesn't exist in the response.
XMLHttpRequest.open()
Initializes a request. This method is to be used from JavaScript code; to initialize a request from native code, use openRequest() instead.
XMLHttpRequest.overrideMimeType()
Overrides the MIME type returned by the server.
XMLHttpRequest.send()
Sends the request. If the request is asynchronous (which is the default), this method returns as soon as the request is sent.
XMLHttpRequest.setRequestHeader()
Sets the value of an HTTP request header. You must call setRequestHeader()after open(), but before send().

Non-standard methods

XMLHttpRequest.init()
Initializes the object for use from C++ code.
Warning: This method must not be called from JavaScript.
XMLHttpRequest.openRequest()
Initializes a request. This method is to be used from native code; to initialize a request from JavaScript code, use open() instead. See the documentation for open().
XMLHttpRequest.sendAsBinary()
A variant of the send() method that sends binary data.

Specifications

Specification Status Comment
XMLHttpRequest Living Standard Live standard, latest version

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support1 Yes17 Yes1.2
onreadystatechange112171 Yes1.2
readyState11217 Yes1.2
response Yes12 Yes ? Yes Yes
responseText Yes12 Yes ?2 Yes10
responseType3112610187
responseURL371432 No248
responseXML Yes12 Yes3 Yes Yes Yes
status112171 Yes1.2
statusText112171 Yes1.2
timeout2912128

17

12 — 16

Yes
upload112 Yes ? Yes10
withCredentials Yes123.54105124
abort112 Yes

7

56

Yes1.2
getAllResponseHeaders11247

7

56

Yes1.2
getResponseHeader112 Yes7

7

56

Yes1.2
open112 Yes8

7

56

Yes1.2
overrideMimeType112 Yes

11

56

Yes1.2
send1121

7

56

Yes1.2
sendAsBinary No9 No2 — 31 No No No
setRequestHeader112 Yes

7

56

Yes1.2
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes1124 Yes ? Yes
onreadystatechange11 Yes4 Yes ? Yes
readyState Yes1 Yes4 Yes ? Yes
response Yes Yes Yes Yes Yes ? Yes
responseText Yes Yes Yes Yes Yes ? Yes
responseType5555 Yes50 Yes ?6.0
responseURL3737 ?3224 ? Yes
responseXML Yes Yes Yes Yes3 Yes Yes Yes
status Yes Yes Yes4 Yes ? Yes
statusText Yes1 Yes4 Yes ? Yes
timeout Yes Yes Yes Yes Yes ? Yes
upload Yes1 ? ? Yes ? Yes
withCredentials Yes Yes ?44 Yes ? Yes
abort Yes Yes Yes Yes Yes ? Yes
getAllResponseHeaders Yes Yes Yes47 Yes ? Yes
getResponseHeader Yes1 Yes Yes7 Yes ? Yes
open Yes1 Yes Yes8 Yes Yes Yes
overrideMimeType Yes1 Yes Yes Yes Yes Yes
send Yes1 Yes4 Yes Yes Yes
sendAsBinary No9 No9 No4 — 31 No No No
setRequestHeader Yes1 Yes Yes Yes Yes Yes

1. Internet Explorer version 5 and 6 supported ajax calls using ActiveXObject()

2. Before IE 10, the value of XMLHttpRequest.responseText could be read only once the request was complete.

3. Prior to Firefox 51, an error parsing the received data added a <parsererror> node to the top of the Document and then returned the Document in whatever state it happens to be in. This was inconsistent with the specification. Starting with Firefox 51, this scenario now correctly returns null as per the spec.

4. Starting with Firefox 11, it's no longer supported to use the withCredentials attribute when performing synchronous requests. Attempting to do so throws an NS_ERROR_DOM_INVALID_ACCESS_ERR exception.

5. Internet Explorer versions 8 and 9 supported cross-domain requests (CORS) using XDomainRequest

6. Implemented via ActiveXObject

7. Starting from Firefox 49, empty headers are returned as empty strings in case the preference network.http.keep_empty_response_headers_as_empty_string is set to true, defaulting to false. Before Firefox 49 empty headers had been ignored. Since Firefox 50 the preference defaults to true.

8. Starting in Firefox 30, synchronous requests on the main thread have been deprecated due to their negative impact on performance and the user experience. Therefore, the async parameter may not be false except in a Worker.

9. There is a polyfill available to support sendAsBinary().

See also

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 Last updated by: SteveVS,