⚡ Fast2D

The best 2D physics for JavaScript — fast, lightweight, and intuitive.

fast2d.com · zero dependencies · TypeScript-first · renderer-agnostic

Fast2D is the fastest, most lightweight, and most intuitive 2D physics engine for JavaScript. The core is pure, allocation-conscious TypeScript with no runtime dependencies and no rendering baked in — drive it with WebGPU, WebGL, or a Canvas2D fallback. The long-term scope grows from rigid bodies to soft bodies to fluids, with cross-platform deterministic simulation for lockstep/rollback multiplayer.

Quick start

npm install fast-2d

import { World, Bodies } from "fast-2d";

const world = new World({ gravity: [0, 9.81] });
const ball = world.add(Bodies.circle({ position: [0, 0], radius: 0.5 }));
world.add(Bodies.rectangle({ position: [0, 10], width: 20, height: 1, isStatic: true }));

world.step(1 / 60);
console.log(ball.position.y);

Positions accept a Vec2, a [x, y] tuple, or { x, y } — whatever reads best.

Compound bodies

Concave rigid bodies are authored as one body with multiple convex parts:

import { Bodies, plus } from "fast-2d";

const custom = Bodies.compound({
	position: [0, -2],
	parts: [
		{ type: "rectangle", width: 0.4, height: 2.4 },
		{ type: "rectangle", width: 0.8, height: 0.4, center: [-0.6, 0] },
		{ type: "rectangle", width: 0.8, height: 0.4, center: [0.6, 0] },
	],
});

const cross = plus({ position: [2, -2], width: 2, height: 2, thickness: 0.4 });

Parts should be non-overlapping convex polygons/circles, and dynamic compounds must be authored with their total center of mass at the body origin. Convenience builders (plus, cross, lShape, arrow, star) are standalone named exports so unused shapes can tree-shake away.

Why Fast2D?

• Fast — allocation-free hot paths, precomputed inverse mass/inertia, a data-oriented solver.
• Lightweight — zero runtime dependencies, tree-shakeable ESM + CJS, ships types.
• Intuitive — a tiny, well-documented API (World, Bodies, Body, Vec2).
• Renderer-agnostic — the core never touches the DOM; you own the pixels.

Docs

• Getting Started
• fast2d.com — live demos and benchmarks

License

Fast2D is free for noncommercial use under the PolyForm Noncommercial License 1.0.0.

Commercial use requires a separate license. If you want to use Fast2D in or for a for-profit business, product, or service, get a commercial license or written permission first — email [email protected] or use the form at fast2d.com/contact.

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