Create a Mod

The Create a Mod wizard automates the process of creating and configuring a new mod. It:

• Creates a new mod under steamapps\SourceMods\
• Dumps the C++ source code to a location of your choosing
• Registers your mod with the SDK launcher

You will need to restart Steam for a new mod to appear in your library.

Engine branch

Before starting a mod you need to choose which version of Source you will use. Change the SDK's engine version to the one you want.

Source 2006

A very outdated version that only exists it the SDK for backwards compatibility reasons. Don't choose it unless you really have to.

Source 2007

Slightly outdated, but the most recent HL2-compatible engine branch that provides source code. This is what most mods use. Note: 27/02/11. Compatible to make any mods until 2009 SDK is released.

Source 2009

The latest HL2-compatible build of Source, but without available source code. The wizard will break if you invoke it for 2009; you can make a content-only mod of a 2009 game, but you will have to create it manually.

Alien Swarm (via Alien Swarm SDK)

The oddball of the bunch. Alien Swarm is totally free to play and its SDK includes source code, but it's source code for a top-down shooter. It also lacks many of the HL2-compatible code's peripheral tools (including custom shader support) and cannot access HL2's content.

The SDK wizard

Project type

This section does not apply to Alien Swarm.

When you start the wizard you will have to choose which Visual Studio projects you want it to give you.

Half-Life 2 Single Player

Projects for Episode One (2006) or Two (2007). If you do not own Ep1/2 this option will be greyed out.

Half-Life 2 Multiplayer

Half-Life 2: Deathmatch.

Confirm:Only available if you own HL2DM.

Multiplayer mod from template

A specially-created SDK project that demonstrates how Valve implement common multiplayer features. You can configure some extra settings from the wizard.

Source code only

Dumps the code without creating an actual mod. This handy if you are only creating a server plugin.

Whichever option you choose, you get the same actual source code files (even if you didn't own one or another game). You also get an "everything" solution which includes a collection of development tools.

Mod Information

The first option on this page is where you want the source code extracted to. The second is the name you want to use, which also defines the output folder for your compiled content (does not appear if you chose source code only).

Creating a mod manually

It's surprisingly simple:

1. Create a folder under steamapps\SourceMods\ (A mod can actually reside anywhere, but placing it here allows Steam to detect and launch it.)
2. Create a gameinfo.txt in the folder. You now have a mod!
3. Open the SDK launcher and switch to the relevant engine branch.
4. Choose "Edit Game Configurations" and click "Add". Enter your mod's name and folder.

To get the source code (or indeed any other files of Valve's that you want to modify) you will need to use GCFScape and access sourcesdk.gcf\src_mod\. Remember to change the custom build steps to point to your mod's folder.