browserSettings.overrideContentColorScheme

A BrowserSetting object whose underlying value is a string.

Firefox enables users to choose a theme for the browser UI. These themes apply either a light or dark theme to webpages. Using the layout.css.prefers-color-scheme.content-override preference, users can override the theme and choose to render webpages in a light or dark theme or follow the device's theme. This browser setting exposes that preference.

This object takes these values:

• "light": Applies a light theme to webpages.
• "dark": Applies a dark theme to webpages.
• "system": Applies a light or dark theme to webpages based on the device's theme.
• "browser": Applies a light or dark theme to webpages based on the browser's theme.

function logResult(result) {
  console.log(`Setting was modified: ${result}`);
}

browser.browserSettings.overrideContentColorScheme
  .set({ value: "dark" })
  .then(logResult);