It’s super easy to detect whether a user has their device set to Dark or Light mode using a CSS media query.

@media (prefers-color-scheme: dark) {
	/* Styles for users who prefer dark mode */
}

@media (prefers-color-scheme: light) {
	/* Styles for users who prefer light mode */
}

You should only need to use one of these queries, as the user will default to the code outside of the media query if the condition isn’t met.

Robin Rendle provides some further advice on how to adjust your content for Dark Mode. It’s not as simple as white text on a black background.

Browser support is pretty much universal.