Steam is the game delivery service where (Including other games) Garry's Mod can be purchased, downloaded, and played. Another use of Steam is downloading items from the workshop, like addons, dupes, saves, and demos. Another use of Steam is to have the Steam cloud sync the configuration files, dupes, saves, demos the player created to other machines when the user logs in to them. Steam is also used to store achievement data for Garry's Mod.

Steam was launched on September 2003 and is the most famous platform for the distribution of PC games and is bundled with automatic updates and an anti-cheat.