Changing website favicon dynamically

Here’s some code that works in Firefox, Opera, and Chrome (unlike every other answer posted here). Here is a different demo of code that works in IE11 too. The following example might not work in Safari or Internet Explorer.

/*!
 * Dynamically changing favicons with JavaScript
 * Works in all A-grade browsers except Safari and Internet Explorer
 * Demo: http://mathiasbynens.be/demo/dynamic-favicons
 */

// HTML5™, baby! http://mathiasbynens.be/notes/document-head
document.head = document.head || document.getElementsByTagName('head')[0];

function changeFavicon(src) {
 var link = document.createElement('link'),
     oldLink = document.getElementById('dynamic-favicon');
 link.id = 'dynamic-favicon';
 link.rel = 'shortcut icon';
 link.href = src;
 if (oldLink) {
  document.head.removeChild(oldLink);
 }
 document.head.appendChild(link);
}

You would then use it as follows:

var btn = document.getElementsByTagName('button')[0];
btn.onclick = function() {
 changeFavicon('http://www.google.com/favicon.ico');
};

Fork away or view a demo.

jQuery Version:

$("link[rel='shortcut icon']").attr("href", "favicon.ico");

or even better:

$("link[rel*='icon']").attr("href", "favicon.ico");

Vanilla JS version:

document.querySelector("link[rel='shortcut icon']").href = "favicon.ico";

document.querySelector("link[rel*='icon']").href = "favicon.ico";

If you have the following HTML snippet:

<link id="favicon" rel="shortcut icon" type="image/png" href="favicon.png" />

You can change the favicon using Javascript by changing the HREF element on this link, for instance (assuming you're using JQuery):

$("#favicon").attr("href","favicon2.png");

You can also create a Canvas element and set the HREF as a ToDataURL() of the canvas, much like the Favicon Defender does.

Why not?

var link = document.querySelector("link[rel~='icon']");
if (!link) {
    link = document.createElement('link');
    link.rel = 'icon';
    document.getElementsByTagName('head')[0].appendChild(link);
}
link.href = 'https://stackoverflow.com/favicon.ico';