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 24, 2026Also documented for this game on ProtonDB · checked Nov 9, 2026
Safe
mangohud %command%Copy
Show the MangoHud performance overlay (Linux)
Effect
Draws FPS, frame timing and CPU/GPU load over Vulkan and OpenGL games. MangoHud runs the game, so %command% is what it runs.
Proton-Deck
MangoHudAdded Jun 29, 2026Last checked Sep 24, 2026Also documented for this game on ProtonDB · checked Nov 9, 2026
Safe
-dx11Copy
Use the DirectX 11 renderer (Unreal Engine games)
Effect
Selects DX11 as the RHI. Ignored by builds without a DX11 path.
Display
UniversalAdded Jun 27, 2026Last checked Sep 27, 2026
Safe
-dx12Copy
Use the DirectX 12 renderer (Unreal Engine games)
Effect
Selects DX12 as the RHI. Ignored by builds without a DX12 path.
Display
UniversalAdded Jun 27, 2026Last checked Sep 24, 2026
Safe
-fullscreenCopy
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 27, 2026
Safe
-hCopy
Set the window height in pixels
Effect
Forces the game to start at the given vertical resolution instead of the saved or auto-detected one.
Example
-w 1920 -h 1080
Display
UniversalAdded Jun 27, 2026Last checked Sep 24, 2026
Safe
-ResX=1920Copy
Set the window width in pixels (Unreal Engine games)
Effect
Takes its value with = and no space. Epic pairs it with -ResY and -windowed.
Example
-windowed -ResX=1920 -ResY=1080
Display
Unreal EngineAdded Aug 11, 2026Last checked Sep 24, 2026
Safe
-ResY=1080Copy
Set the window height in pixels (Unreal Engine games)
Effect
Takes its value with = and no space. Epic pairs it with -ResX and -windowed.
Example
-windowed -ResX=1920 -ResY=1080
Display
Unreal EngineAdded Aug 11, 2026Last checked Sep 24, 2026
Safe
-USEALLAVAILABLECORESCopy
Use all available CPU cores (Unreal Engine games)
Effect
Lifts a core-count limit the engine would otherwise apply. Epic documents it as "Use all available cores."
Forces the game to start at the given horizontal resolution instead of the saved or auto-detected one. Pass -h as well to set height explicitly; on its own, height is derived from the aspect ratio.
Example
-w 1920 -h 1080
Display
UniversalAdded Jun 27, 2026Last checked Sep 24, 2026
Safe
-windowedCopy
Run in windowed mode (Unreal Engine and Source games)
Effect
Unreal documents pairing it with an explicit resolution. In Source -window, -sw and -startwindowed are the same option.
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.
