Detect if the browser is using dark mode and use a different favicon

Adding and removing an icon from the document’s head works in Firefox but not Safari:

• Demo: https://zesty-soybean.glitch.me/
• Source: https://glitch.com/edit/#!/zesty-soybean

Chrome is still implementing (prefers-color-scheme: dark), so the jury’s still out. https://crbug.com/889087. In Chrome 76 with --enable-blink-features=MediaQueryPrefersColorScheme, this correctly sets the icon when the page is loaded, but does not respond dynamically to changes in dark mode.

Safari adds a grey background to dark icons in dark mode (for example, Wikimedia Foundation, Github), so this workaround isn't necessary for legibility.

1. Add two link rel=icon elements with ids for later:

   <link rel="icon" href="a.png" id="light-scheme-icon">
   <link rel="icon" href="b.png" id="dark-scheme-icon">
   

2. Create a CSS media matcher:

   matcher = window.matchMedia('(prefers-color-scheme: dark)');
   matcher.addListener(onUpdate);
   onUpdate();
   

3. Add/remove the elements from the document's head:

   lightSchemeIcon = document.querySelector('link#light-scheme-icon');
   darkSchemeIcon = document.querySelector('link#dark-scheme-icon');
   
   
   function onUpdate() {
   if (matcher.matches) {
   lightSchemeIcon.remove();
   document.head.append(darkSchemeIcon);
   } else {
   document.head.append(lightSchemeIcon);
   darkSchemeIcon.remove();
   }
   }
   

To make it a little more generic than Josh's answer, try this whilst the browsers still get around to implementing media natively. (Notice no hardcoded number of themes, ids, or media-queries in the JS; it's all kept in the HTML.)

<link rel="icon" href="/favicon.ico?light" media="(prefers-color-scheme:no-preference)">
<link rel="icon" href="/favicon.ico?dark"  media="(prefers-color-scheme:dark)">
<link rel="icon" href="/favicon.ico?light" media="(prefers-color-scheme:light)">

$(document).ready(function() {
if (!window.matchMedia)
return;


var current = $('head > link[rel="icon"][media]');
$.each(current, function(i, icon) {
var match = window.matchMedia(icon.media);
function swap() {
if (match.matches) {
current.remove();
current = $(icon).appendTo('head');
}
}
match.addListener(swap);
swap();
});
});

The upshot is that once that attribute is supported, you just need to remove the Javascript and it'll still work.

I deliberately split /favicon.ico?light into two tags instead of a single one with media="(prefers-color-scheme: no-preference), (prefers-color-scheme:light)" because some browsers that don't support media permanently pick the first rel="icon" they see… and others pick the last!

CSS has a theme mode detection using prefers-color-scheme media feature:

@media (prefers-color-scheme: dark) {
...
}

With that in mind, nowadays you can use an SVG as a favicon for your website:

<link rel="icon" href="/favicon.svg" type="image/svg+xml">

Then you can update the SVG favicon design using the CSS prefers-color-scheme media feature. Below is an SVG rectangle with rounded corners, which has a different color, depending on the active theme:

<svg width="50" height="50" viewBox="0 0 50 50" xmlns="http://www.w3.org/2000/svg">
<style>
rect {
fill: green;
}
@media (prefers-color-scheme: dark) {
rect {
fill: red;
}
}
</style>
<rect width="50" height="50" rx="5"/>
</svg>

Now, considering the current browser support for the SVG favicon, a fallback is required for the older browsers:

<link rel="icon" href="/favicon.svg" type="image/svg+xml">
<link rel="icon" href="/favicon.png" type="image/png">
<!-- favicon.ico in the root -->

From https://catalin.red/svg-favicon-light-dark-theme/

Here's a demo too: https://codepen.io/catalinred/pen/vYOERwL

The easiest option is to change the source when you change the mode on your computer.

var element = document.querySelector("link[rel='icon']");
const darkModeListener = (event) => {
if (event.matches) {
console.log("dark");
element.setAttribute("href","img/favicon-dark.svg");
} else {
console.log("light");
element.setAttribute("href","img/favicon-light.svg");
}
};


// Update favicon on Mode change
window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', darkModeListener);


// Check Mode on load
if (window.matchMedia && window.matchMedia('(prefers-color-scheme:      dark)').matches) {
element.setAttribute("href","img/favicon-dark.svg");
} else {
element.setAttribute("href","img/favicon-light.svg");
}

But if you have a multi-device favicon then you need to do something like this ...

// Switch Favicon on Dark/Light Mode
let colorSchemeQueryList = window.matchMedia('(prefers-color-scheme: dark)');
const setColorScheme = e => {
if (e.matches) {
// Dark
var favicon = document.querySelectorAll('link[data-type="favicon"]');
var i = favicon.length;
while (i--) {
favicon[i].setAttribute('href', favicon[i].dataset.dark);
}
} else {
// Light
var favicon = document.querySelectorAll('link[data-type="favicon"]');
var i = favicon.length;
while (i--) {
favicon[i].setAttribute("href", favicon[i].dataset.light);
}
}
}
           

setColorScheme(colorSchemeQueryList);
colorSchemeQueryList.addListener(setColorScheme);

<link rel="apple-touch-icon" sizes="180x180" href="Images/favicon/light/apple-touch-icon.png" data-type="favicon" data-light="Images/favicon/light/apple-touch-icon.png" data-dark="Images/favicon/dark/apple-touch-icon.png">
<link rel="icon" type="image/png" sizes="32x32" href="Images/favicon/light/favicon-32x32.png" data-type="favicon" data-light="Images/favicon/light/favicon-32x32.png" data-dark="Images/favicon/dark/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="Images/favicon/light/favicon-16x16.png" data-type="favicon" data-light="Images/favicon/light/favicon-16x16.png" data-dark="Images/favicon/dark/favicon-16x16.png">
<link rel="favicon" href="Images/favicon/light/site.webfavicon" data-type="favicon" data-light="Images/favicon/light/site.webfavicon" data-dark="Images/favicon/dark/site.webfavicon">
<link rel="mask-icon" href="Images/favicon/light/safari-pinned-tab.svg" color="#000000" data-type="favicon" data-light="Images/favicon/light/safari-pinned-tab.svg" data-dark="Images/favicon/dark/safari-pinned-tab.svg">