XMLHttpRequest.open()

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

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

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.

See also

• Using XMLHttpRequest
• Related XMLHttpRequest methods: setRequestHeader(),send(), and abort()