Reactor multiplayer engine for Unity Free to develop locally. Free to self-host up to 32 CCU. Cloud hosting from $20/mo. See pricing →
Build the multiplayer game
your engine said you couldn't.
You shouldn't have to shrink your game design to fit your netcode. Reactor makes sure you don't: it compresses your traffic automatically, with no serialization code to write.
Survivors demo 4 players 5,000 enemies 15 Hz send rate 50 to 70 KB/s per player
Efficient out of the box.
In a controlled benchmark, Reactor moved 17x less transform data than Unity's Netcode for GameObjects and 9.5x less than Photon Fusion 2. Wire bandwidth, including protocol overhead, was about 6x lower at typical loads.
Click to deploy. Nothing to babysit.
Publish a server image from the Unity editor and launch it on Reactor Cloud. Matchmaking, scaling, and persistent data are part of the hosted service. Use Unity physics or a physics engine of your choice.
Unity editor → live server
- Ctrl+F2Build server configs
- Reactor → Start Local ServerTest on your machine
- Reactor → PublishingPublish the server image
- Reactor → ServersLaunch an instance
- KS Reactor Unity SDK
- Component sync for transforms, animation, physics, and custom properties on any Unity game object.
- KS Reactor Server
- C# runtime: server-authoritative physics, room scripts, tick-rate control, cluster persistence.
- KS Reactor Cloud
- Managed hosting with matchmaking, region selection, and automatic scaling. From $20/mo. Replaces: Photon Cloud, Normcore
- Multi-threaded physics
- Unity physics on parallel server threads with deterministic ticks. Hundreds of concurrent simulations.
- Cluster and room messaging
- Cross-room RPCs and shared cluster state. Sharded MMOs without a custom messaging layer.
Built to scale
Compression covers bandwidth. These engine systems cover large object counts and high player counts.
- Sync groups and interest management
- Each player receives updates only for nearby entities. Per-player bandwidth stays flat as the world grows.
- Server-authoritative physics
- Raycasts, sweeps, and overlap queries run on the server. Hit detection does not depend on what the client reports.
- Built-in prediction and interpolation
- Predictors interpolate motion between server snapshots, and reconciliation against the server is built into the engine.
- Turn single-player into multiplayer
- Add transform, animation, and ownership sync components to the controller you already have. The same code runs on the client and the server.
One player in a world of thousands of entities receives updates from the active sync groups only.
Case study
2 years to build a game, 3 days to add multiplayer
Matt Van Alstyne is building Mutant Mayhem, his first Unity game, alone. Multiplayer was not in the plan.
- Design in one evening, implementation in about two and a half days
- Second player, enemies, upgrades, building, turrets, public lobby, in that order.
- A 4-player match on day three
- The stress test ran with his phone as the authoritative host: 60 to 20 fps at the busiest points, and the match stayed in sync.
- Server authority next, without a rewrite
- Session validation, spawn validators, and reconnect handling, added to the same codebase.
Built with KinematicSoup tools
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Recognition
Start building. No credit card required.
Free to develop locally and to self-host up to 32 CCU. Cloud hosting starts at $20 a month.
Survivors demo · 5,000 enemies · 15 Hz send rate · 50 to 70 KB/s per player