Photon Quantum 3 is now a Unity Verified Solution. Photon Quantum is a deterministic multiplayer engine for Unity. Instead of syncing object state, it sends only player inputs over the network and runs the identical simulation on every client. Clients predict ahead and roll back when real inputs arrive. Quantum is built for competitive, latency-sensitive games such as fighting, sports and esports-style titles, and for games that want strong protection against state manipulation without running dedicated servers.
Every client runs the same deterministic simulation from the same inputs. Only those inputs travel over the network. State is computed locally on each machine.
To keep controls responsive, each client doesn’t wait for everyone’s input. It predicts the inputs it hasn’t received yet and advances the simulation. When the confirmed inputs arrive and differ from the prediction, Quantum rolls back to the last confirmed frame and resimulates. This reduces perceived input latency and holds up well on higher-latency connections. Network conditions still matter, though: large or frequent mispredictions show up as corrections.
The simulation runs independently of Unity’s frame rate, and the same simulation code can be used for single-player and multiplayer modes.
Quantum provides deterministic libraries for math, 2D and 3D physics and navigation, but determinism also depends on your gameplay code. Simulation code has to follow Quantum’s rules: memory-aligned C#, no untracked randomness, and no floating-point operations that could diverge across hardware. Code that breaks these rules can still desync.
If your team wants to write ordinary Unity gameplay code without those constraints, Photon Fusion fits Unity’s normal workflow more directly.
Because every client computes state from inputs, state-injection cheats like speed hacks or health hacks are rejected by the deterministic engine itself. That gives cheat resistance against state manipulation comparable to a dedicated server, without the infrastructure bill.
The trade-off is information. Every client holds the full game state, so genres where hidden information matters, like fog of war or hidden hands, need to account for that exploit risk. For extra checks, an optional server-side plugin can verify the simulation.
Besides the deterministic math, physics and navigation libraries, Quantum ships with a Kinematic Character Controller (KCC) and a Bots SDK. Its Unity integration includes a performance profiler covering simulation and network usage, the Quantum Hub for project setup, CodeDoc inspectors for generated code, data-driven system setup, and entity views for inspecting entity state.
For online play, Quantum runs on Photon Cloud, so you don’t host game servers yourself. Pricing is based on peak CCU (concurrent users, the number of players connected at the same moment). Development is free on the 20 CCU development tier. One live commercial Fusion or Quantum game per customer can run on a free 100 CCU tier, which is hard-capped. Multiplayer pricing made simple covers the paid tiers.
The best place to start is the Quantum Asteroids tutorial, followed by the Simple Brawler video series. Other samples cover specific genres: Blueless (2D platformer), Twin Stick Shooter (twin-stick controls and AI), QBall (sports), Karts (racing physics), Racer 2.5D, Motor Dome (vehicle combat), Quantum XR and Bots (AI-driven gameplay).
The Photon Quadrant explained compares Quantum with Fusion’s three topologies.
Photon’s first attempt at deterministic multiplayer was Photon TrueSync in 2015. It taught the team what a deterministic engine needed, and in 2017 the first version of Photon Quantum shipped, built on a deterministic Entity Component System (ECS). Quantum 3 is the result of years of iteration on that foundation, and it’s now a Unity Verified Solution.
Games shipping on Photon Quantum include Songs of Silence (Chimera Entertainment), 33 Immortals (Thunder Lotus), Windblown (Motion Twin) and Bandit Trap (Picomy).
Photon Video is now available to every developer with Photon Voice & Video 2.64. Add live video streams and screen sharing to Unity apps on phones, desktops, XR headsets and smart glasses, using one Video App ID for video and voice.
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Our CEO/CTO Christof Wegmann sat down with GodotFest co-founder Johannes Ebner to talk about Godot's growth, why we built Fusion for Godot, and what to expect in Munich on November 3 & 4.
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