The XMLHttpRequest method open() initializes a newly-created request, or re-initializes an existing one.

Note: Calling this method for an already active request (one for which open() has already been called) is the equivalent of calling abort().

Syntax

XMLHttpRequest.open(method, url)
XMLHttpRequest.open(method, url, async)
XMLHttpRequest.open(method, url, async, user)
XMLHttpRequest.open(method, url, async, user, password)

Parameters

method
The HTTP request method to use, such as "GET", "POST", "PUT", "DELETE", etc. Ignored for non-HTTP(S) URLs.
url
A DOMString representing the URL to send the request to.
async Optional
An optional Boolean parameter, defaulting to true, indicating whether or not to perform the operation asynchronously. If this value is false, the send() method does not return until the response is received. If true, notification of a completed transaction is provided using event listeners. This must be true if the multipart attribute is true, or an exception will be thrown.
Note: Synchronous requests on the main thread can be easily disruptive to the user experience and should be avoided; in fact, many browsers have deprecated synchronous XHR support on the main thread entirely. Synchronous requests are permitted in Workers.
user Optional
The optional user name to use for authentication purposes; by default, this is the null value.
password Optional
The optional password to use for authentication purposes; by default, this is the null value.

Specifications

Specification Status Comment
XMLHttpRequest
The definition of 'open()' in that specification.
Living Standard WHATWG living standard

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 1Edge Full support 12Firefox Full support Yes
Notes
Full support Yes
Notes
Notes 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.
IE Full support 7
Full support 7
Full support 5
Notes
Notes Implemented via ActiveXObject
Opera Full support YesSafari Full support 1.2WebView Android Full support YesChrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support Yes
Notes
Full support Yes
Notes
Notes 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.
Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support
See implementation notes.
See implementation notes.

See also

Document Tags and Contributors

Contributors to this page: Narvey, mfuji09, Sheppy, ExE-Boss, wbamberg, Makyen, erikadoyle, teoli, Majr, nadih, MashKao, jsx
Last updated by: Narvey,