s&box is a modern game engine built on Valve's Source 2 and the latest .NET technology, offering a modern intuitive editor for creating games, and it is aimed at game creators who want to build and play games inside an engine that runs live, alongside the contributors who compile the engine itself from source.

What it is

s&box is a game engine and editor written in C#, built on top of Valve's Source 2 and current .NET technology. It sits in two ecosystems at once: the Source 2 engine lineage and the .NET toolchain, which together supply the rendering and platform foundations as well as the C# authoring layer that developers work in. The project spans a public repository holding the engine source, a website at sbox.game, developer documentation, forums, and a Steam distribution channel, with the topic tags gamedev, sbox and source2 marking its position.

The concrete problem it solves is access. Getting at Source 2 technology normally means going through Valve's own tooling and titles, while this repository publishes the engine source so that anyone willing to build it can compile the engine and editor from the public tree rather than obtaining the toolchain exclusively as a finished binary. For game creators, the practical replacement is the getting started guide and Steam download; for contributors, the repository itself replaces the closed state of the engine by shipping the files needed to produce working game and editor binaries locally. Bugs and feature requests have their own tracker in the sbox-issues repository, separate from the source tree.

Key capabilities

• A modern editor for creating games, available both through Steam as app 590830 and through the project at sbox.game.
• The complete engine source, cloneable from https://github.com/Facepunch/sbox-public.git and built by running Bootstrap.bat, which downloads dependencies and builds the engine.
• Build prerequisites of Git, Visual Studio 2026 and the .NET 10 SDK, indicating a Windows-oriented C# development workflow.
• Runnable game and editor binaries produced under the game folder once the build completes.
• Documentation covering tutorials and API references at sbox.game/dev, with a first-steps getting started guide.
• Contributing process described in CONTRIBUTING.md, with issue reporting routed to sbox-issues.
• A layered licence structure: MIT for the engine source, the s&box EULA for native binaries in game/bin, and third-party components enumerated in game/thirdpartylegalnotices.

Who uses it and how

• Game creators start with the getting started guide at sbox.game/dev/doc/about/getting-started/first-steps/ and install the editor through Steam, which is the supported path for making games rather than building the engine.
• Engine contributors clone the repository, install Visual Studio 2026, Git and the .NET 10 SDK, then run Bootstrap.bat to compile and test the editor locally, following the contributing guide.
• Bug reporters and feature requesters use the sbox-issues repository, which carries a large open backlog, so triage rather than instant turnaround should be expected.
• Community members gather on the forums at sbox.game/f/ and the main site for news, with documentation serving as the reference layer for API work.

Getting started

Install the s&box editor directly from Steam, or compile the engine from source by cloning https://github.com/Facepunch/sbox-public.git and running Bootstrap.bat with Git, Visual Studio 2026 and the .NET 10 SDK present.

How it compares

This registry entry does not name any paid products that s&box replaces, so no licence, self-hosting or cost comparison against commercial alternatives is made here. Among similar tools, the only engine the facts name is Valve's Source 2, which is the foundation s&box is built upon rather than a competitor. On the evidence provided, s&box stands alone in this registry.

When to use it — and when not to

A self-hoster or contributor must operate a Windows build environment with Visual Studio 2026 and the .NET 10 SDK, and must accept that the compiled result mixes MIT-licensed source with binaries governed by the s&box EULA and separately licensed third-party components. Anyone who simply wants to make a game should take the Steam route and skip the source build entirely, since the repository is explicitly intended for engine development rather than game authoring. The project also carries a substantial open issue count, and its licence metadata is recorded as NOASSERTION, so users wanting a single uncomplicated licence should read LICENSE.md and the third-party notices carefully before committing.

# Clone the repo
git clone https://github.com/Facepunch/sbox-public.git