Box2D is a 2D physics engine for games (by erincatto)

Box2D Alternatives

Similar projects and alternatives to Box2D

NOTE: The number of mentions on this list indicates mentions on common posts plus user suggested alternatives. Hence, a higher number means a better Box2D alternative or higher similarity.

Box2D reviews and mentions

Posts with mentions or reviews of Box2D. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2024-04-17.
  • Blaze: A High Performance C++ Math library
    7 projects | | 17 Apr 2024
    For typical game physics engines... not that much. Math libraries like Eigen or Blaze use lots of template metaprogramming techniques under the hood that can help when you're doing large batched matrix multiplications (since it can remove temporary allocations at compile-time and can also fuse operations efficiently, as well as applying various SIMD optimizations), but it doesn't really help when you need lots of small operations (with mat3 / mat4 / vec3 / quat / etc.). Typical game physics engines tend to use iterative algorithms for their solvers (Gauss-Seidel, PBD, etc...) instead of batched "matrix"-oriented ones, so you'll get less benefits out of Eigen / Blaze compared to what you typically see in deep learning / scientific computing workloads.

    The codebases I've seen in many game physics engines seem to all roll their own math libraries for these stuff, or even just use SIMD (SSE / AVX) intrinsics directly. Examples: PhysX (, Box2D (, Bullet (

  • Jolt Physics raylib: trying 3D C++ Game Physics Engine
    1 project | | 10 Apr 2024
    Box2D: 2D engine used in Unity and also earlier versions of Godot. Open source.
  • Rust Game Physics Engines: PhysX, Rapier, XPBD & Others
    10 projects | | 3 Apr 2024
    Box2D GitHub repo: erincatto/box2d
  • Nebula is an open-source and free-to-use modern C++ game engine
    6 projects | | 9 Jan 2024
  • Linear code is more readable
    3 projects | | 14 Sep 2023
    Why is 600 lines too long? How are you able to make that judgment call without first knowing what the algorithm is even doing? People setting arbitrary limits like this is what leads to convoluted spaghetti, instead of just taking things on a case by case basis. Here’s a function from the Box2D code running a particularly complex algorithm for solving contact velocities .

    It’s 310 lines long. It reads very well, and it looks very maintainable. It has very clear comments explaining the reasoning behind the harder parts of the code. Would you reject this code because it’s pretty long? I wouldn’t.

    There is no such thing as too long or too short. There’s overengineered and there’s underengineered and there’s a sweet spot in the middle that has the perfect amount of engineering with the least amount of complexity (preferably no additional complexity than the original problem warranted). Sometimes, the problem at hand is inherently a large algorithm and requires many lines of code. Don’t split it up! It just makes it harder for future maintainers who now have to figure out if the additional functions are actually being used elsewhere or if they’re just there to make the code “pretty”.

  • How would you implement a simple collision system?
    1 project | /r/cpp_questions | 17 Jul 2023
    There is always the approach of looking at how an existing engine is implemented, such as box2d:
  • C++23: The Next C++ Standard
    8 projects | | 11 Jul 2023
    TIL Box2D must not be serious code because it doesn't use copious amounts of explicit temporaries[0].

    And just for the record, I'm very glad Erin Catto decided to use operator overloading in his code. It made it much easier for me to read and understand what the code was doing as opposed to it being overly verbose and noisy.


  • Make a game engine in C++
    4 projects | /r/learnprogramming | 10 Jul 2023
    For Physics Box2d can be used as a simple starting point.
  • Does anyone know any good open source project to optimize?
    8 projects | /r/cpp | 7 Jun 2023
    I suspect most C++ physics libraries like Box2D ( or Bullet3 ( could really benefit a lot from SIMD.
  • what to start learning
    5 projects | /r/GraphicsProgramming | 28 Apr 2023
    for 2D physics have a look at Box2D it's amazing
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Basic Box2D repo stats
2 months ago

erincatto/box2d is an open source project licensed under MIT License which is an OSI approved license.

The primary programming language of Box2D is C++.

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