Reactor multiplayer engine Free to develop locally. Free to self-host up to 32 CCU. See pricing →
Build the multiplayer game
your engine said you couldn't.
At least 9.5x better transform compression than Photon Fusion 2 and Netcode for GameObjects. Around 6x lower wire bandwidth overall. The gap widens as your scene gets denser, the point where other engines start to saturate the network.
Better transform compression than Photon Fusion 2 and Netcode for GameObjects. Wire bandwidth runs about 6x lower at typical loads. The ratio improves further as your scene gets denser.
See the bandwidth comparison →Built to scale
Low bandwidth alone won't carry you beyond 1,000 CCU. Reactor backs the compression with the engine systems that make large object counts and high concurrency work in production.
Sync groups and interest management
Spatially partition entities so each player only receives updates for what's relevant to them. Your world can grow without your bandwidth growing with it.
Server-authoritative physics
Raycasts, sweeps, and overlap queries all run as real physics on the server. The client is never trusted to report its own hits.
Built-in prediction and interpolation
Customizable predictors smooth motion and properties between server snapshots. Reconciliation against the server ships with the engine, so it isn't something you build yourself.
Turn single-player into multiplayer
Drop component-based transform, animation, and ownership sync onto a single-player controller you already have. There's no rewrite, and no separate client and server codepaths to keep in sync.
Ship now. Harden later.
Most multiplayer engines force a choice up front: easy-to-build client authority, or secure-but-rigid server authority. Reactor lets you start fast and add validation when you actually need it, without rewriting your game.
Client-authoritative
Drop ownership and sync components onto your existing Unity controller. Get to playtest fast with no server-side rewrites.
Inject server validation
Add server-side property validators that intercept and filter client updates before replication. No architectural changes.
Full server authority
Migrate to server-driven physics with tick-based simulation and input prediction. Same framework, no rewrite.
ksValidationResult ValidateProperty(
uint propertyId,
ksMultiType value,
float deltaTime)
{
if (value.Float > maxSpeed)
return ksValidationResult.FAIL; // reject
return ksValidationResult.PASS; // accept
}
Server-side validation, dropped in when cheating becomes worth solving.
The new benchmark for snapshot replication
Snapshot-based replication is usually pitched for shooters, but it fits persistent worlds, physics sandboxes, and strategy games just as well.
High-CCU shooters and battle royales
Server-authoritative input, hit-scan and projectile, multi-threaded controllers. Tested past 1,000 CCU.
Persistent worlds and MMOs
Rooms run for months at a time. Cluster persistence and cross-room messaging for sharded worlds.
Crowds, sims, and physics-driven games
Sync hundreds of dynamic entities at 2 bytes per update. Every interaction is driven by the physics simulation rather than canned animation.
RTS, sandboxes, and strategy
Dense object counts that would saturate other netcodes. 120Hz tick rates available where you need them.
Trusted by studios using Reactor in production
A full stack for
real-time multiplayer.
Reactor is a full multiplayer platform. It includes the server runtime, the client SDK, physics integration, and cloud hosting, and every layer is swappable. Run cloud-hosted or self-hosted, and bring your own physics or use ours.
KS Reactor Unity SDK
Component-based sync for transforms, animations, physics, and custom properties. Works with any Unity controller, any lifecycle.
KS Reactor Server
C# server runtime with server-authoritative physics, custom room scripts, tick-rate control, and cluster-level persistence.
KS Reactor Cloud
Managed hosting with zero-config matchmaking, region selection, and automatic scaling. Free up to 32 CCU.
Replaces: Photon Cloud, Normcore
Multi-threaded physics
Server runs Unity physics on parallel threads with deterministic tick timing. Scale to hundreds of concurrent simulations.
Cluster and room messaging
Cross-room RPCs and persistent state across the cluster. Build sharded MMOs without a custom messaging layer.
Self-hostable, no lock-in
Run the server runtime on your own infrastructure. Docker images, Linux binaries, Kubernetes-ready.
Replaces: Unity Relay, Photon SaaS lock-in
Also from KinematicSoup
Scene Fusion: real-time Unity co-editing
Multiple developers editing the same scene at the same time, live. Scene Fusion syncs transforms, prefab edits, and terrain changes across the team as you work.
Recognition
Start building. No credit card required.
Free to develop locally. Free to self-host up to 32 CCU. Upgrade when your player count does.