P2P rollback netcode library for browser-based multiplayer games
npm install rollback-netcode
> Note: This library is under active development. APIs may change.
A TypeScript library for P2P rollback netcode in browser-based multiplayer games. Supports 4+ players with WebRTC—no dedicated server required.
Live Demo | API Reference | FAQ
- Rollback netcode - Simulate optimistically, rollback and resimulate on misprediction
- N-player support - 4+ players, not limited to 2
- P2P networking - WebRTC DataChannels, works in any modern browser
- Dynamic join/leave - Players can join or leave during gameplay
- Desync detection - Periodic state hashing with automatic recovery
- Transport-agnostic - WebRTC included, or bring your own
``bash`
npm install rollback-netcode
Your game must implement four methods:
`typescript
import type { Game, PlayerId } from 'rollback-netcode';
class MyGame implements Game {
private state = { x: 100, y: 100 };
serialize(): Uint8Array {
const buffer = new ArrayBuffer(8);
const view = new DataView(buffer);
view.setFloat32(0, this.state.x);
view.setFloat32(4, this.state.y);
return new Uint8Array(buffer);
}
deserialize(data: Uint8Array): void {
const view = new DataView(data.buffer, data.byteOffset, data.byteLength);
this.state.x = view.getFloat32(0);
this.state.y = view.getFloat32(4);
}
step(inputs: Map
for (const [, input] of inputs) {
if (input[0] & 0x01) this.state.x -= 5; // left
if (input[0] & 0x02) this.state.x += 5; // right
if (input[0] & 0x04) this.state.y -= 5; // up
if (input[0] & 0x08) this.state.y += 5; // down
}
}
hash(): number {
return Math.floor(this.state.x * 1000 + this.state.y);
}
}
`
`typescript
import { createSession, WebRTCTransport } from 'rollback-netcode';
const transport = new WebRTCTransport('my-player-id');
transport.setSignalingCallbacks({
onSignal: (peerId, signal) => {
// Send signal to peer via your signaling server
signalingServer.send(peerId, signal);
}
});
// Handle incoming signals from your signaling server
signalingServer.onSignal((fromPeerId, signal) => {
if (signal.type === 'description') {
transport.handleRemoteDescription(fromPeerId, signal.description);
} else {
transport.handleRemoteCandidate(fromPeerId, signal.candidate);
}
});
const session = createSession({ game: new MyGame(), transport });
session.on('playerJoined', (player) => console.log(${player.id} joined));`
session.on('desync', () => console.log('Desync detected, recovering...'));
`typescript
// Host creates a room
const roomId = await session.createRoom();
// Others join
await session.joinRoom(roomId, hostPeerId);
`
`typescript
session.start(); // Host only
function gameLoop() {
const input = new Uint8Array([
(keys.left ? 0x01 : 0) |
(keys.right ? 0x02 : 0) |
(keys.up ? 0x04 : 0) |
(keys.down ? 0x08 : 0)
]);
session.tick(input);
render(game);
requestAnimationFrame(gameLoop);
}
`
See the examples/` directory:
- local-transport - Browser demo using simulated network (no server needed)
- webrtc - Real WebRTC connections with a minimal signaling server
- API Reference - Full API documentation
- FAQ - Common questions answered
- Architecture - Technical design and components
- Configuration Tuning - Performance tuning guide
- Node.js >= 22.0.0 (development)
- Modern browser with WebRTC (Chrome 56+, Firefox 44+, Safari 11+, Edge 79+)