Valve is dedicated to providing the best tools and resources for the modding community. The Source engine and SDK give you all the tools you need to produce brilliant game creations.

The Source SDK is available free of charge via Steam with purchase of a Source-based game, such as Half-Life 2 or Team Fortress 2. Learn more about building Source-powered mods at

(1) Garry’s Mod (Team Garry). (2) The Ship (Outerlight). (3) Day-of-Defeat: Source.

Do you teach game design?

SourceU, a new educational licensing program, bundles Valve's game development technologies and other resources. Click here to learn more.