Left 4 Dead 2

How to apply a launch option on Steam

1. Open Steam and go to your Library.
2. Right-click the game and choose Properties.
3. On the General tab, find the Launch Options field.
4. Type or paste the option (e.g. -windowed) into the field. To use several at once, separate them with spaces (e.g. -windowed -novid).
5. Close Properties. Steam saves automatically, and the option applies next time you launch the game.

To remove one, reopen the same field and delete the text. Options are game-specific; an option that helps one game may do nothing (or misbehave) in another.

Worth knowing: a launch option can break a game's rendering, reset local settings, or trip anti-cheat in multiplayer. Read the description first, add one at a time, and treat anything rated above Safe as a deliberate experiment.