Welcome to the Valve Developer Community. Whether you're building a "Triple-A" commercial project or a MOD for Half-Life® 2, you'll want to sign up as a Valve developer today.
Source and the Source SDK
Our knowledgebase of technical information about using the engine and all of the related tools is now posted on a community-driven web site called a WIKI. Sign up as a developer to contribute or to ask a question.
For MOD Teams
Why choose the Source Engine for your MOD?
New Steam client
Japanese Documentation Project Underway
Source Engine AI Debugging