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



XMLHttpRequest Standard (XMLHttpRequest)
# states

Browser compatibility

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