Web/API/XMLHTTPRequest/open

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[, 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
XMLHttpRequestThe definition of 'open()' in that specification.	Living Standard	WHATWG living standard

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`open`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1 Notes' Full support 1 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 5	Opera Full support 8	Safari Full support 1.2	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4 Notes' Full support 4 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 10.1	Safari iOS Full support 1	Samsung Internet Android Full support 1.0

Legend

Full support: Full support
See implementation notes.': See implementation notes.