How to detect timeout on an AJAX (XmlHttpRequest) call in the browser?


Solution 1

UPDATE: Here's an example of how you can handle a timeout:

var xmlHttp = new XMLHttpRequest();"GET", "", true);

   if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
// Now that we're ready to handle the response, we can make the request
// Timeout to abort in 5 seconds
var xmlHttpTimeout=setTimeout(ajaxTimeout,5000);
function ajaxTimeout(){
   alert("Request timed out");

In IE8, You can add a timeout event handler to the XMLHttpRequest object.

var xmlHttp = new XMLHttpRequest();
xmlHttp.ontimeout = function(){
  alert("request timed out");

I would recommend against making synchronous calls as your code implies and also recommend using a javascript framework to do this. jQuery is the most popular one. It makes your code more efficient, easier to maintain and cross-browser compatible.

Solution 2

Some of the modern browsers (2012) do this without having to rely on setTimeout: it's included in the XMLHttpRequest. See answer

var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
    if (xhr.readyState == 4) {
        alert("ready state = 4");
};"POST", "", true);
xhr.setRequestHeader("Content-type", "application/json; charset=utf-8");
xhr.timeout = 4000;
xhr.ontimeout = function () { alert("Timed out!!!"); }

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Updated on January 17, 2020


  • Mike
    Mike almost 4 years

    I'm looking on the web, but documentation is hard to come by. We all know the basic AJAX call using the browser's built-in XMLHttpRequest object (assume a modern browser here):

    var xmlHttp = new XMLHttpRequest();  // Assumes native object"GET", "", false);
    var statusCode = xmlHttp.status;
    // Process it, and I'd love to know if the request timed out

    So, is there a way that I can detect that the AJAX call timed out by inspecting the XMLHttpRequest object in the browser? Would I be advised to do something like window.setTimeout(function() { xmlHttp.abort() }, 30000);?



  • Jose Gómez
    Jose Gómez about 9 years
    In 2014, this answer should be tagged as the correct one. Nowadays, almost any browser supports this (even IE8 onwards).
  • KevinHJ
    KevinHJ over 7 years
    Well, not quite - be warned that ontimeout event does not get fired until AFTER readyState == 4 is triggered. This is not only non-intuitive, but makes it difficult to create conditional behavior based on whether an upload didn't succeed due to the fact that there was a timeout or not. For example, customizing a user alert as to the reason an upload failed. In my situation I found that I could only accomplish what I wanted with setTimeout. Also, xhr.timeout does not seem to work on Safari as of 2016.
  • Antonio Cañas Vargas
    Antonio Cañas Vargas over 3 years
    In my case, part of a page is updated when the user changes any option in a form. For this I use the onclick and onchange events and an AJAX object. What I want is to display an alert when the network goes offline, so that users get feedback that their changes have not been saved. If I disconnect the network, the solution based on "setTimeout" works; the one based on "ontimeout" does not work.
  • Peter Quiring
    Peter Quiring over 2 years
    ontimeout was only added to Chrome in version 91. Debian is only at version 90 as of now.