Dark theme can be easier to see, and it can save battery on some screens.
Not all browsers offer this kind of extensions.
Chrome extension
In the chrome extension market, you can install Dark Theme:
And activate by clicking on the Power button:
Firefox extension
In the firefox extension market, you can install Dark Reader:
And activate by clicking on the On button:
Safari extension
In the Apple App Store, you can install Eclipse, then enable it in the Safari settings:
