The XMLHttpRequest.readyState property returns the state an XMLHttpRequest client is in. An XHR client exists in one of the following states:

Value State Description
0 UNSENT Client has been created. open() not called yet.
1 OPENED open() has been called.
2 HEADERS_RECEIVED send() has been called, and headers and status are available.
3 LOADING Downloading; responseText holds partial data.
4 DONE The operation is complete.
The XMLHttpRequest client has been created, but the open() method hasn't been called yet.
open() method has been invoked. During this state, the request headers can be set using the setRequestHeader() method and the send() method can be called which will initiate the fetch.
send() has been called and the response headers have been received.
Response's body is being received. If responseType is "text" or empty string, responseText will have the partial text response as it loads.
The fetch operation is complete. This could mean that either the data transfer has been completed successfully or failed.

The state names are different in versions of Internet Explorer earlier than 11. Instead of UNSENT, OPENED, HEADERS_RECEIVED, LOADING and DONE, the names READYSTATE_UNINITIALIZED (0), READYSTATE_LOADING (1), READYSTATE_LOADED (2), READYSTATE_INTERACTIVE (3) and READYSTATE_COMPLETE (4) are used.


var xhr = new XMLHttpRequest();
console.log('UNSENT', xhr.readyState); // readyState will be 0

xhr.open('GET', '/api', true);
console.log('OPENED', xhr.readyState); // readyState will be 1

xhr.onprogress = function () {
    console.log('LOADING', xhr.readyState); // readyState will be 3

xhr.onload = function () {
    console.log('DONE', xhr.readyState); // readyState will be 4



Specification Status Comment
XMLHttpRequest Living Standard WHATWG living standard

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
readyStateChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 7Opera Full support 8Safari Full support 1.2WebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support 10.1Safari iOS Full support 1Samsung Internet Android Full support 1.0
constantsChrome Full support YesEdge Full support 12Firefox Full support 9IE Full support 9Opera Full support 12Safari Full support YesWebView Android Full support YesChrome Android Full support 18Firefox Android Full support 9Opera Android Full support YesSafari iOS ? Samsung Internet Android Full support 1.0


Full support
Full support
Compatibility unknown
Compatibility unknown