2D Physics Engines: 5 Best for Indie Developers
Most indie developers never pick a 2D physics engine directly — they use whatever their game engine bundles, and what most of them bundle is Box2D. Unity, GDevelop, GameMaker, and Construct all run their 2D physics on Box2D, the C++ standard Erin Catto released in 2007; Godot is the exception, shipping its own engine. If you are choosing a library, the five that matter are Box2D for the standard, Godot Physics 2D for engine-native convenience, Rapier for modern cross-platform determinism, Matter.js for the friendliest web start, and Chipmunk2D for lightweight native work. This guide ranks them, compares language, license, and platform, and tells you which one fits which indie situation — and where a 2D-first IDE like Egmatic fits if you want the physics and the engine in one tool.
Most indie developers never pick a 2D physics engine directly — they use whatever their game engine already bundles, and what most of them bundle is Box2D. Unity, GDevelop, GameMaker, and Construct all build their 2D physics on Box2D, the C++ library Erin Catto first released in 2007; Godot is the notable exception, shipping its own engine. So the real question is rarely "which physics engine is best" in the abstract. It is "which one fits my platform, and does my engine already give me a good one." The five libraries below are the ones worth knowing, ranked for indie work in 2026.
| Engine | Language | License | Best for |
|---|---|---|---|
| Box2D | C++ | MIT | The standard — most engines run on it |
| Godot Physics 2D | C++ (inside Godot) | MIT | Staying native to Godot |
| Rapier | Rust (WASM) | Apache-2.0 | Modern native + web, determinism |
| Matter.js | JavaScript | MIT | Browser games, the easiest start |
| Chipmunk2D | C | MIT | Lightweight portable native games |
The framing: most indies inherit their physics
Before the per-engine breakdown, one fact saves a lot of effort. The mainstream 2D engines do not make you choose a physics library — they ship one:
| Game engine | 2D physics it runs on |
|---|---|
| Unity | Box2D |
| Godot | Godot Physics 2D (its own engine) |
| GameMaker | Box2D |
| Construct | Box2D |
| GDevelop | Box2D |
| MonoGame | None bundled — you add a library |
If you are already in one of these, the default answer is to use the engine's built-in physics. You reach for a standalone library only when you are writing your own game on a framework (MonoGame), targeting the browser directly, or chasing a feature your engine lacks. With that settled, here is how the five compare.
Box2D — the standard
Box2D is the C++ rigid-body physics engine Erin Catto created and released in 2007, and it is the closest thing 2D games have to a shared standard. Unity, GameMaker, Construct, and GDevelop all run their 2D physics on it, so if you have learned "how 2D physics works" in any of those tools, you have largely learned Box2D. It is fast, stable, well-documented, and deliberately limited to rigid bodies — no fluids or soft bodies out of the box. It supports continuous collision detection for fast-moving objects, which lighter engines skip. The current version 3 is a ground-up rewrite in C with a focus on performance. If you are choosing a library and have no reason to pick otherwise, Box2D is the default that is hard to regret.
Godot Physics 2D — the engine-native exception
Godot is the mainstream engine that does not run on Box2D by default. Its built-in 2D physics is its own engine, Godot Physics 2D, reached through the PhysicsServer2D API and nodes such as RigidBody2D, StaticBody2D, and Area2D. The advantage is tight integration — physics speaks Godot's scene and node model natively, and because Godot is free and MIT-licensed with no royalties, there is no commercial ceiling. Box2D and Rapier exist for Godot as third-party extensions, so if you specifically need Box2D's behavior you can add it, but most Godot 2D games simply use the built-in engine and never look elsewhere. The trade-off is the usual engine-native one: your physics is bound to Godot.
Rapier — the modern cross-platform choice
Rapier is the youngest engine on this list, written in Rust with WebAssembly bindings, and it handles both 2D and 3D in one library. Its standout feature is a deterministic mode: given the same inputs, it produces the same outputs across machines, which is what keeps a physics simulation in sync across a multiplayer network. It runs in the browser through WASM and natively through Rust, which makes it a natural fit for a modern stack that may span both. For an indie choosing a library rather than inheriting one, Rapier is the forward-looking pick — modern codebase, active development, and the determinism that networked games eventually demand. Its license is the permissive Apache-2.0.
Matter.js — the friendly web option
Matter.js is a 2D physics engine written in pure JavaScript, and it is the friendliest way to put physics in a browser game. The API is clear, the documentation is good, and you can have bodies falling and colliding in an afternoon. Its limits are the limits of a lightweight library: it lacks continuous collision detection, so fast projectiles can tunnel through thin walls, and it is tuned for browser performance rather than heavy scenes. For a casual web game, a prototype, or anything where ease of starting matters more than raw capability, Matter.js is the right first choice. When you outgrow it, the upgrade path on the web is Planck.js or Rapier.
Chipmunk2D — the lightweight native library
Chipmunk2D is a 2D rigid-body physics library written in C by Scott Lembcke, and it is the lightweight native alternative to Box2D. It is small, portable, and easy to embed in a C or C++ project that does not need everything Box2D carries. Its main limitation, like Matter.js, is the absence of continuous collision detection, which matters for shooters, pinball, and anything with fast-moving thin objects but not for slower games. For a native project that values a small dependency footprint over feature completeness, Chipmunk2D is a solid, mature choice under the MIT license.
Honorable mentions
Two libraries round out the picture without making the top five. Planck.js is a JavaScript port of Box2D, so when you need Box2D's feature set and speed in a browser but do not want the Rust-and-WASM setup of Rapier, it is the direct route. LiquidFun, Google's extension to Box2D, added particle-based fluid and soft-body physics on top of the standard rigid-body engine — powerful for the niche that needs it, but it is less actively maintained than the core engines above and is a specialized tool rather than a general one.
How to pick by your situation
- You are in Unity, GameMaker, GDevelop, or Construct → use the built-in physics. It is Box2D, and the integration is already done.
- You are in Godot → use Godot Physics 2D. Add a Box2D extension only if you specifically need Box2D behavior.
- You are writing a browser game in JavaScript → start with Matter.js for ease, move to Planck.js or Rapier-WASM when you need more.
- You need deterministic physics for multiplayer → Rapier, for its deterministic mode.
- You are on a Rust or WebAssembly stack → Rapier.
- You are writing native C/C++ and want minimal dependencies → Chipmunk2D, or Box2D if you want the full standard.
- You are on MonoGame → there is no bundled physics, so add a C# Box2D port such as Velcro or Aether.Physics2D.
Common mistakes
| Mistake | What goes wrong | What to do instead |
|---|---|---|
| Choosing a library when your engine already bundles one | Unnecessary integration work and a second physics system to maintain | Use the built-in physics unless you have a concrete reason not to |
| Assuming Godot uses Box2D | Wrong mental model; behavior differs from Unity/Box2D docs | Know Godot ships its own engine; consult Godot's physics docs |
| Picking Matter.js for a fast shooter | Projectiles tunnel through walls — no CCD | Use a library with continuous collision detection (Box2D, Rapier, Planck.js) |
| Ignoring determinism for multiplayer physics | Desync between clients | Pick Rapier's deterministic mode, or authoritate physics server-side |
| A web-only library for a console/desktop target | No native build for your platform | Match the library's platform support to your release targets |
How Egmatic fits
For most of the situations above, the physics engine is already decided — the real work is tuning it, and tuning is a loop. Change a body's mass, run the scene, watch whether the crate settles or bounces, adjust, repeat. The engine choice matters less than how fast that loop closes.
Egmatic is built to close it. Its 2D physics runs inside the same editor as the scene and the logic, with live preview, so you adjust a collider or a material constant and see the result in seconds rather than rebuilding. Because physics, scene composition, and the event logic that reacts to collisions are all one tool, there is no hand-off between a physics editor and the rest of the project. If your goal is to finish a 2D game with physics that feel right rather than to assemble and integrate a physics toolchain, that is the shorter path.
Conclusion
The best 2D physics engine for an indie is usually the one already in your game engine — Box2D, for Unity, GameMaker, Construct, and GDevelop; Godot Physics 2D, for Godot. Of the standalone libraries, Box2D is the safe standard, Rapier is the modern cross-platform choice with a deterministic mode that suits multiplayer, Matter.js is the easiest way into a browser game, and Chipmunk2D is the lightweight native option. Planck.js and LiquidFun fill the web-Box2D and fluid-simulation niches. Pick by your platform and language first, match the library's feature set — especially continuous collision detection and determinism — to your game, and remember that the engine you run on matters less than a fast loop for tuning it. For the primitives you tune — rigid bodies, colliders, triggers — see the 2D game physics guide; for how the engine under them works, the 2D physics engine overview covers the pipeline.
Sources
- Box2D is a free, open-source 2D rigid-body physics engine created by Erin Catto, first released in 2007, MIT license; version 3 is a C rewrite — Box2D.org and Wikipedia: Box2D
- Unity's 2D physics runs on Box2D; the standard Rigidbody2D and Collider2D components use it, and Unity 6.3 added a separate low-level 2D physics API built on Box2D version 3, leaving the existing components unchanged — Unity Discussions: Low-level 2D Physics in Unity 6.3
- Godot's default 2D physics is its own engine (Godot Physics 2D / PhysicsServer2D); Box2D is available only as a third-party extension — Godot documentation: Physics in 2D and godot-box2d extension
- Rapier is an open-source 2D and 3D physics engine written in Rust with WebAssembly bindings and a deterministic mode; licensed Apache-2.0 — Rapier.rs and @dimforge/rapier2d-deterministic on npm
- Matter.js is a 2D physics engine for the browser, written in JavaScript, MIT license — Matter.js
- Chipmunk2D is a lightweight 2D rigid-body physics library written in C by Scott Lembcke, MIT license — Chipmunk2D
- Planck.js is a JavaScript port of Box2D for the web, MIT license — Planck.js on GitHub
- LiquidFun is Google's extension to Box2D adding particle-based fluid and soft-body physics — LiquidFun
- GameMaker, GDevelop, and Construct build their 2D physics features on Box2D — GameMaker: Physics, GDevelop: Physics behavior, Construct: Physics
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