MavonEngine is an open-source Three.js game engine built for single player or real-time multiplayer. It combines rendering, physics, networking, animation, and debugging into a single cohesive TypeScript package — so you're not assembling a stack, you're building a game.
Early WIP — things will change. For documentation visit mavonengine.com.
npx @mavonengine/cli create my-gameThis downloads the multiplayer template, installs it, starts the game server and opens the game in your browser, with a live dashboard of the server in the terminal.
Everything runs on one port: the game server serves the client (with hot reload in dev) and the game socket next to its own API.
| URL | Description |
|---|---|
| http://localhost:8050/ | Client game |
| http://localhost:8050/#debug | Debug mode: debug UI and the server's physics colliders |
| http://localhost:8050/api/game/health | Server health endpoint |
Press . in the game to open the level editor.
The multiplayer template includes the authoritative server setup, networking boilerplate, and a working client/server split out of the box.
MavonEngine is a full-stack Three.js game engine built on top of Three.js for rendering, Rapier3D for physics, and geckos.io for WebRTC-based UDP networking.
Most Three.js game engines focus on single-player or leave multiplayer as an exercise for the developer. MavonEngine is designed from the ground up for multiplayer — with a unified server-client architecture, authoritative physics, and real-time networking built in, not bolted on.
The core is a headless BaseGame class that both client and server extend from. The server runs
physics and the game loop without rendering. The client extends it with Three.js rendering, camera,
audio, and input. Because both sides share the same entity classes and loop, game logic is written
once and shared — the authoritative server syncs state down to clients each tick.
The server runs a simplified hitbox scene alongside the client's full 3D world, enabling server-side hit detection, raycasting, and spatial queries without trusting the client. This makes it viable for competitive PvP games, open-world multiplayer, and physics-based action games.
The networking model is inspired by Source engine architecture — a tick-based command buffer with server-authoritative state, distance-based entity culling, hash-based change detection, and bandwidth tracking. The client maintains a WebRTC connection via geckos.io with ping monitoring and state reconciliation.
- Three.js rendering — Custom GLSL shader support, wireframe/armature/physics debug overlays
- Rapier3D physics — Kinematic character controller, collider management, real-time debug visualization
- WebRTC networking — Real-time data channels, bandwidth monitoring, command buffering
- Shared entity system — Write once, run on server and client
- Skeletal animation — GLTF + Draco support, smooth fade transitions, efficient skeleton cloning
- Particle system — Built-in rain and smoke effects, custom shader support
- Level editor — Early WIP, loads directly from the running game instance and stays connected to the server
- Scenes — JSON scene files shared by client and server; each side builds only what it needs, and the server reloads a scene when the editor saves it
- Prefab registry — Community-built assets (grass, water, and more) ready to drop into your scene
- Engine plugins —
mavonengine installadds plugins with their client, server and asset parts;mavonengine buildships only the assets your game uses - Gamepad support — Xbox, PlayStation and generic controllers with deadzones, button labels and rumble
- Monitoring —
mavonengine dashboardin the terminal, or the@mavonengine/http-monitoringplugin in the browser: tick time, CPU, bandwidth, players, logs and HTTP requests - Latency simulation — Test your netcode against artificial latency, jitter and packet loss
- AI assistant support (MCP) —
mavonengine mcplets any MCP client and model inspect the running game: server metrics, scenes and entities, the browser tabs' renderer stats, console and screenshots, and one entity compared on server and client. It also reads the documentation on mavonengine.com - Full TypeScript — Comprehensive types throughout
Projects created with mavonengine create include a .mcp.json, so MCP clients that read it (such as Claude Code)
pick up the MavonEngine MCP server automatically. For other clients (Cursor, VS Code, Codex, Gemini CLI, Zed, …),
register it as a stdio server:
{
"mcpServers": {
"mavonengine": { "command": "npx", "args": ["-y", "@mavonengine/cli", "mcp"] }
}
}Every tool is read-only. Scene, entity and client tools only work in development; the docs tools read the live documentation on mavonengine.com. See the CLI README for the full list.
Three.js is the most widely used 3D library for the web, but it's a rendering library — not a game engine. MavonEngine fills that gap specifically for single or multiplayer: entity management, state machines, world/chunk streaming, input handling, resource loading, and authoritative networking are all handled for you.
This is early-stage software built out of real project needs. APIs will change and some parts are still tightly coupled to specific setups. Contributions and PRs are welcome — see the contributing guide to get started.
Join the community for development discussions.