Chaos Source Engine

Chaos Source is a branch of Valve Software's Source Engine based off Counter‑Strike: Global Offensive.

The main goal of Chaos Source is to provide a shared engine base for many different Source Engine projects, so that those mods can benefit from each other instead of every team having to implement the same features independently.

Engine FAQ

Why is it not open source?

We're big fans of open source, but since Chaos Source uses licensed source code, the engine code cannot be open sourced.

This is however the only code that cannot be open sourced. All of our other tools like, for example, the asset builder, are all open source, if possible.

Do you use leaked code?

No. All of our projects are green-lit, licensed and endorsed by Valve. We do not use any leaked code and will never leak ourselves.

Is there an SDK?

No. Due to the way source is set up and certain conditions, Chaos Source is only accessible in our games and cannot be distributed as standalone SDK.

If you wish to create a single-player game with Chaos Source features, Portal 2: Community Edition would probably suit your project the best, even for non-portal mods.

Legal Information


Chaos Source uses a custom fork of the Qt UI framework for several tool applications. Qt is licensed under the LGPLv3 license, see this page for more info. Qt's source code can be obtained here or from this GitHub repository.