Select Page

Detect System Theme Preference Change Using JavaScript

David Walsh
Published: October 24, 2022

JavaScript and CSS allow users to detect the user theme preference with CSS’ prefers-color-scheme media query. It’s standard these days to use that preference to show the dark or light theme on a given website. But what if the user changes their preference while using your app?

To detect a system theme preference change using JavaScript, you need to combine matchMedia, prefers-color-scheme, and an event listener:

window.matchMedia('(prefers-color-scheme: dark)')
      .addEventListener('change',({ matches }) => {
  if (matches) {
    console.log("change to dark mode!")
  } else {
    console.log("change to light mode!")
  }
})

The change event of the matchMedia API notifies you when the system preference changes. You can use this event to automatically update the site’s display in real time.

I love that this API allows detecting user preference on a system level. Catering to user needs is an important part of creating a great web experience!

  • Create Spinning Rays with CSS3: Revisited
  • CSS @supports

    Feature detection via JavaScript is a client side best practice and for all the right reasons, but unfortunately that same functionality hasn’t been available within CSS.  What we end up doing is repeating the same properties multiple times with each browser prefix.  Yuck.  Another thing we…

  • CSS :target

    One interesting CSS pseudo selector is :target.  The target pseudo selector provides styling capabilities for an element whose ID matches the window location’s hash.  Let’s have a quick look at how the CSS target pseudo selector works! The HTML Assume there are any number of HTML elements with…

  • CSS Background Animations


Source: davidwalsh.name