Press Alt+Enter while you’re playing a full-screen game to enable windowed mode. You can press the shortcut again to switch out of windowed mode and re-enable full-screen mode, too.
This keyboard shortcut doesn’t work in every PC game. It’s up to the game’s developer to support it, but it does work in a wide variety of games—both modern PC games and older Windows PC games going back to the 90s.
If this keyboard shortcut doesn’t work in the game you’re currently playing, you’ll need to open the PC game’s graphics settings window and choose full-screen or windowed mode instead.
This keyboard shortcut even works in some applications that aren’t games. For example, in Command Prompt, Windows PowerShell, and the new Windows Terminal, you can press Alt+Enter to toggle between full-screen and windowed modes for your terminal.
Of course, many other desktop applications, including web browsers, use F11 to toggle between full-screen and windowed modes instead.