Run in fullscreen mode (Unreal Engine and Source games)
Effect
Overrides a saved windowed preference. -full is the same option in Source.
Display
UniversalAdded Jun 27, 2026Last checked Sep 12, 2026
Safe
gamemoderun %command%Copy
Run the game under Feral GameMode (Linux)
Effect
Applies temporary host optimisations (CPU governor, I/O and process priority) for the game's lifetime, then restores them on exit. GameMode runs the game, so %command% is what it runs.
Proton-Deck
Feral GameModeAdded Jun 29, 2026Last checked Sep 12, 2026
Safe
PROTON_USE_D9VK=1 %command%Copy
Use DXVK for Direct3D 9 (obsolete) (Linux, Proton 4.x and earlier)
Effect
Valve marks it obsoleted as of Proton 5.0 — DXVK became the default for d3d9, so on any current Proton this does nothing. In older versions it selected Vulkan-based DXVK over OpenGL-based wined3d.
On the General tab, find the Launch Options field.
Type or paste the option (e.g. -windowed) into the field. To use several at once, separate them with spaces (e.g. -windowed -novid).
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.
