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The XMLHttpRequest.open() method initializes a request. This method is to be used from JavaScript code; to initialize a request from native code, use openRequest() instead.

Note: Calling this method for an already active request (one for which open() or openRequest() has already been called) is the equivalent of calling abort().
void open(
   DOMString <var>method</var>,
   DOMString <var>url</var>,
   optional boolean <var>async</var>,
   optional DOMString <var>user</var>,
   optional DOMString <var>password</var>
The HTTP method to use, such as "GET", "POST", "PUT", "DELETE", etc. Ignored for non-HTTP(S) URLs.
The URL to send the request to.
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: Starting with Gecko 30.0 (Firefox 30.0 / Thunderbird 30.0 / SeaMonkey 2.27), synchronous requests on the main thread have been deprecated due to the negative effects to the user experience.
The optional user name to use for authentication purposes; by default, this is an empty string.
The optional password to use for authentication purposes; by default, this is an empty string.


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1 (Yes) 5[1]
(Yes) 1.2
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) 1.0 (Yes) (Yes) (Yes) (Yes)

[1] This feature was implemented via ActiveXObject(). Internet Explorer implements the standard XMLHttpRequest since version 7.

See also

Using XMLHttpRequest


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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

Reference XMLHttpRequest