Detect System Theme Preference Change Using JavaScript

By  on  

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!

Recent Features

  • By
    Send Text Messages with PHP

    Kids these days, I tell ya.  All they care about is the technology.  The video games.  The bottled water.  Oh, and the texting, always the texting.  Back in my day, all we had was...OK, I had all of these things too.  But I still don't get...

  • By
    Interview with a Pornhub Web Developer

    Regardless of your stance on pornography, it would be impossible to deny the massive impact the adult website industry has had on pushing the web forward. From pushing the browser's video limits to pushing ads through WebSocket so ad blockers don't detect them, you have...

Incredible Demos

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!