Box2D

June 8, 2026 · View on GitHub

Box2D is a 2D physics engine for games.

Features

Collision

Continuous collision detection
Contact events
Convex polygons, capsules, circles, rounded polygons, segments, and chains
Multiple shapes per body
Collision filtering
Ray casts, shape casts, and overlap queries
Sensor system

Physics

Robust Soft Step rigid body solver
Continuous physics for fast translations and rotations
Island based sleep
Revolute, prismatic, distance, mouse joint, weld, and wheel joints
Joint limits, motors, springs, and friction
Joint and contact forces
Body movement events and sleep notification

System

Data-oriented design
Written in portable C17
Extensive multithreading and SIMD
Optimized for large piles of bodies

Samples

OpenGL with GLFW
Graphical user interface with imgui
Many samples to demonstrate features and performance

Building All Platforms

Install CMake
Install git
Ensure these run from the command line

The presets in CMakePresets.json give one build flow on every platform and are picked up automatically by Visual Studio, VS Code, and CLion (open the folder and choose a preset). From the command line:

Windows: cmake --preset windows then cmake --build --preset windows-release
Linux: cmake --preset linux-release then cmake --build --preset linux-release
macOS: cmake --preset macos then cmake --build --preset macos-release

Use the *-debug build presets for a debug build (not recommended for the replay viewer). The presets use the default native toolchain (the installed Visual Studio on Windows, Make on Linux, Xcode on macOS), so no specific compiler version is required.

Building for Visual Studio

Install Visual Studio
Run build_vs2026.bat for Visual Studio 2026, or use the windows preset above for other versions
Open and build the generated solution in the build folder

Building for Linux

Run build.sh from a bash shell
Results are in the build sub-folder

Building for Xcode

mkdir build
cd build
cmake -G Xcode ..
Open box2d.xcodeproj
Select the samples scheme
Build and run the samples

Building and installing

mkdir build
cd build
cmake ..
cmake --build . --config Release
cmake --install . (might need sudo)

Replay viewer

The samples app doubles as a viewer for Box2D recordings (.b2rec files). Any preset above builds it. Pass a recording on the command line to open it directly:

Windows: build\bin\Release\samples.exe path\to\session.b2rec
Linux: build/bin/samples path/to/session.b2rec
macOS: build/bin/Release/samples path/to/session.b2rec

On Windows you can also drag a .b2rec file onto samples.exe. The viewer runs from any directory. Without an argument, open a recording from the Replay menu. See docs/recording.md for how to make a recording.