Official specs from Steam

Garry's Mod system requirements

Minimum and recommended PC specs as listed by the developer on Steam. Native macOS version available. Native Linux build available.

Garry's Mod release infoSteam page Check other games

Minimum

OSWindows® 10
Processor2 GHz Processor or better
Memory4 GB RAM
Graphics1GB dedicated VRAM or better
DirectXVersion 9.0c
NetworkBroadband Internet connection
Storage10 GB available space
Sound CardDirectX® 9 compatible
Additional NotesMouse, Keyboard, Monitor

Recommended

OSWindows® 10/11
Processor2.5 GHz Processor or better
Memory8 GB RAM
Graphics4GB dedicated VRAM or better
DirectXVersion 9.0c
NetworkBroadband Internet connection
Storage25 GB available space

macOS minimum

OSOS X version Snow Leopard 10.6.3
Processor2 GHz Processor or better
Memory4 GB RAM
Graphics1GB dedicated VRAM or better
NetworkBroadband Internet connection
Storage10 GB available space
Additional NotesMouse, Keyboard, Monitor

macOS recommended

OSLatest OS X version
Processor2.5 GHz Processor or better
Memory8 GB RAM
Graphics4GB dedicated VRAM or better
NetworkBroadband Internet connection
Storage25 GB available space

FAQ

What graphics card do I need for Garry's Mod?

Minimum: 1GB dedicated VRAM or better. Recommended: 4GB dedicated VRAM or better.

How much RAM does Garry's Mod need?

Garry's Mod needs 4 GB RAM at minimum, 8 GB RAM recommended.

How big is Garry's Mod?

Garry's Mod requires 10 GB available space.

Does Garry's Mod run on Mac or Steam Deck/Linux?

Yes, there is a native macOS version. A native Linux build is available.