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Enable dark mode in Firefox without changing themes

·242 words·2 mins·

Most modern web browsers, such as Firefox, take cues from the desktop environment or from themes applied to the browser to determine whether a user wants light or dark mode from websites. This is often done through the prefers-color-scheme CSS media feature:

.day   { background: #eee; color: black; }
.night { background: #333; color: white; }

@media (prefers-color-scheme: dark) {
  .day.dark-scheme   { background:  #333; color: white; }
  .night.dark-scheme { background: black; color:  #ddd; }

@media (prefers-color-scheme: light) {
  .day.light-scheme   { background: white; color:  #555; }
  .night.light-scheme { background:  #eee; color: black; }

There are those situations where you want web pages to prefer a dark mode, but you don’t want to change your desktop settings or apply a darker theme to Firefox. You can follow these steps to prefer dark color schemes in Firefox:

  1. Type about:config in the address bar and press enter.
  2. Click Accept the Risk and Continue. (if you want to accept the risk) 😉
  3. In the search box, type ui.systemUsesDarkTheme
  4. Click the Number radio button below the search box.
  5. Press the plus (+) on the far right side.
  6. Set the value to 1 and press enter.

Now, close the about:config page and load up a website that has dark color schemes available.

If you want to test the change quickly, just reload this page! My blog has light and dark color schemes set depending on what your browser prefers. 🎉 😎

Photo credit: Andre Benz on Unsplash