If you have Windows 10, you can turn on chrome dark mode and this will automatically apply dark mode on your applications like Chrome and Firefox.

Open Settings
Personalization
Colors
Default app Mode, Choose Black
Chrome, Firefox and other applications including the setting menu will be set to a dark mode

Use a Google chrome theme for Dark mode:

There’s a Google chrome theme that will put your browser into dark mode. All you need to do is apply it.

Go to Chrome and head over the menu
Click on settings
Appearance
Themes Chose Just black theme
It will be applied immediately

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