lightyear

Multiplayer netcode is the part of game development that quietly kills projects. Lightyear handles it for the Bevy engine: server-authoritative networking for Rust games with client prediction, interpolation, and input handling built in, free and open source.

It's a library, not a service, so there's no infrastructure beyond the game server you were already going to run. Transport is pluggable: UDP, WebSocket, WebTransport (which makes browser builds work), and Steam sockets. Inputs are buffered per tick and protected against packet loss, and there are first-class integrations with leafwing-input-manager and the Avian physics engine.

Bevy developers building anything competitive or physics-heavy should start here instead of rolling their own. The main alternative in the same ecosystem is bevy_replicon, which is simpler but leaves prediction and interpolation to you.

The catch: it moves with Bevy. Every engine release means a migration, the docs are a work-in-progress book, and outside Bevy it's useless to you by design.