Getting Started with Half-Life 2 Modding

Half-Life 2 modding is one of the longest-running modding scenes in PC gaming, with the canonical tools shipped by Valve themselves. This guide walks the standard install of standalone mods and Workshop content.

Step 1 — Install Source SDK Base (if needed)

Some HL2 mods need Source SDK Base 2013 (free, in your Steam library under Tools). Install it before any mod that lists it as a dependency.

Step 2 — Install standalone mods to sourcemods folder

The classic HL2 mod-install path: drop the mod's folder into Steam/steamapps/sourcemods/.

After install, restart Steam. The mod appears as a separate game in your library (under "Tools" or the main games list, depending on Steam version).

Three legendary HL2 mods worth installing:

• MINERVA: Metastasis — a four-chapter unofficial expansion that arguably surpasses Valve's pacing.
• Underhell — psychological horror mod, ambitious scope.
• The Closure — atmospheric short.

Each downloads from ModDB. Extract to sourcemods/.

Step 3 — Steam Workshop subscriptions

For smaller drop-in mods (UI replacers, sound packs, weapon skins):

HL2 Workshop — subscribe, mods auto-install.

Workshop mods don't appear in sourcemods/ — they're loaded into HL2 directly.

Step 4 — Author your own (Source SDK)

Source SDK is free in your Steam Tools library. Launch it to access:

• Hammer — level editor. The same editor Valve used.
• Model Viewer (HLMV) — view and animate models.
• Faceposer — facial animation tool.

The Source SDK documentation on Valve's developer community (developer.valvesoftware.com) is the canonical reference. The Source engine modding documentation hasn't changed substantially in over a decade, which is good — what you learn stays useful.

Step 5 — Multiplayer mods

Synergy is the standout: co-op Half-Life 2. Install from Steam (it's a standalone free download), play HL2's campaign with up to 8 players. Many other mods build on or pair with Synergy.

Common gotchas

• Source SDK Base missing. Some standalone mods require Source SDK Base 2013 in your library, not just installed but actually launched once.
• sourcemods/ folder doesn't exist. Create it. The path is exactly Steam/steamapps/sourcemods/.
• Mod folder name mismatch. Some standalone mods expect specific folder names. Read the README.
• Workshop mod not loading. Workshop mod installs are immediate; restart HL2 if missing.
• Cross-mod conflicts. Standalone mods are isolated, but multiple Workshop mods can conflict on shared assets.

If you mod HL2 and like the engine, the Half-Life: Alyx guide covers Valve's VR-only entry with its own (separate, smaller) modding scene.