How do I turn on dark mode?

You'll be able to: Turn on dark mode across Windows and apps to reduce eye strain

The steps

1
Press the Windows key and the letter I together to open Settings. The Windows Settings window opens on your screen.
Windows Settings window opened to the main categories list.
Screenshot on the way. The steps above are complete without it.
Why use a keyboard shortcut instead of searching?
WinI opens Settings directly from any screen or app in less than a second.
2
Click Personalisation in the left menu, then click Colours. The Colours settings page opens, showing a preview of your desktop theme and accent options.
The Colours settings page showing the Choose your mode dropdown.
Screenshot on the way. The steps above are complete without it.
3
Click the dropdown next to Choose your mode and select Dark. Your taskbar, Start menu, File Explorer, and supported apps immediately switch from bright white to dark grey and black.
Tip
If you only want apps to be dark while keeping your taskbar light, select Custom instead and choose your preference for each.

It looks different on my screen

On Windows 10, open Settings, click Personalisation, select Colours from the left sidebar, and scroll down to Choose your colour to pick Dark.

Did this work?