Half-Life 2 Modding on OpenMods

Valve's modding template made flesh

Half-Life 2 (2004) is Valve's foundational FPS that defined Source-engine modding. The Source SDK ships free with the game and includes everything Valve themselves used to make HL2: Hammer (level editor), modelviewer, materials editor, soundscape editor. Half-Life 2 modding produced a generation of standalone games, Garry's Mod itself started as an HL2 mod.

In 2026 the modding scene is mature, the toolchain has been stable for over 15 years, and the catalogue is huge: total conversions, custom campaigns, gameplay overhauls, multiplayer mods (Synergy for co-op).

The toolchain

• Source SDK: Valve's free SDK. Includes Hammer (level editor), Faceposer, HLMV (model viewer).
• Steam Workshop: primary distribution for smaller mods.
• moddb.com: large legacy mod hub. Major HL2 total conversions live here.
• mods/ folder: drop standalone mods in Steam/steamapps/sourcemods/. They appear in the Steam library.

What you'll find on OpenMods

HL2 mods live primarily on Steam Workshop and ModDB. GitHub is rare for older Source mods. OpenMods catalogues whatever GitHub-published HL2 content exists.

Practical notes

• sourcemods folder is the standard standalone-mod path. Drop a mod's folder here; it appears as a separate game in your Steam library.
• Steam Workshop subscriptions handle smaller drop-in content.
• The Source engine is open-modded. Hammer, HLMV, and Faceposer give you the same tools Valve used.
• HL2: Episodes Pack content available. Some mods require Episodes 1 and 2.