There is a Dark reader addon. Note that it can lower Firefox's performance.

Some site have built-in theme detection based on your operating system settings. If you don't use a dark theme for your OS, there is a way to set Firefox to tell websites you do. This won't cover all sites, but will help with some of them. Here's how:

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(B) In the search box, type or paste ui.systemUsesDarkTheme

(C) Firefox should display a bar with some radio buttons to choose a new preference type, followed by a + button. Choose Number and click the + button:

(D) Edit the value to either 0 (Light) or 1 (Dark) and then click the blue check mark button or press Enter/Return to save the change.

You should noticed a change immediately on the about:config page.

There is a Dark reader addon. Note that it can lower Firefox's performance.

I already used it but I didn't like it tbh.

Some site have built-in theme detection based on your operating system settings. If you don't use a dark theme for your OS, there is a way to set Firefox to tell websites you do. This won't cover all sites, but will help with some of them. Here's how: (A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk. (B) In the search box, type or paste ui.systemUsesDarkTheme (C) Firefox should display a bar with some radio buttons to choose a new preference type, followed by a + button. Choose Number and click the + button: (D) Edit the value to either 0 (Light) or 1 (Dark) and then click the blue check mark button or press Enter/Return to save the change. You should noticed a change immediately on the about:config page.

Omg thank u so much :)

Some site have built-in theme detection based on your operating system settings. If you don't use a dark theme for your OS, there is a way to set Firefox to tell websites you do. This won't cover all sites, but will help with some of them. Here's how: (A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk. (B) In the search box, type or paste ui.systemUsesDarkTheme (C) Firefox should display a bar with some radio buttons to choose a new preference type, followed by a + button. Choose Number and click the + button: (D) Edit the value to either 0 (Light) or 1 (Dark) and then click the blue check mark button or press Enter/Return to save the change. You should noticed a change immediately on the about:config page.

I tried it but it didn't make the google website dark. It is still white and it hurts my eyes especially at night.

See also:

• https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme

But is there a way to make firefox dark other than using extensions like dark reader?