Two common formats:

Once you find 10 or 15 tweaks you like, don't re-download them every time you reinstall Windows. Do this instead:

Forces a dark theme on built-in Windows apps and the shell.

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Themes\Personalize]
"AppsUseLightTheme"=dword:00000000
"SystemUsesLightTheme"=dword:00000000

10 Registry Tweaks Github: Windows

Two common formats:

Once you find 10 or 15 tweaks you like, don't re-download them every time you reinstall Windows. Do this instead:

Forces a dark theme on built-in Windows apps and the shell.

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Themes\Personalize]
"AppsUseLightTheme"=dword:00000000
"SystemUsesLightTheme"=dword:00000000