Photon Fusion 2.1 for Unity is now Stable

Photon Fusion 2.1 Stable is now available.

This release adds new functionality for teams building state-synchronized multiplayer games with Fusion, with a particular focus on Shared Authority, physics handling, bandwidth control, reconnect behavior, and runtime configuration.

The main additions include:

• Forecast Physics
• Object Priority
• Large Data RPCs
• Improved Master Client switching
• Configurable Shared Mode tickrate and send rate
• Input Delay for Host and Server Mode
• PlayerUniqueId
• Server Mode cloud connection recovery
• Updated Fusion 2.1 samples

Download Fusion 2.1 Stable
Download Fusion 2.1 Stable from the Unity Asset Store
Read the full Fusion 2.1 release notes

What Changed in Fusion 2.1

Fusion 2.1 extends Fusion’s state synchronization model with features that address common production problems in multiplayer game development: physics simulation quality, object prioritization, reconnect flows, bandwidth use, and session continuity.

For projects using Shared Mode, this release is especially relevant. Shared Mode games often need to run without a dedicated game server while handling authority, physics objects, and real-time interaction. Fusion 2.1 adds several tools aimed at making those scenarios easier to build and tune.

The release also includes improvements for Host and Server Mode projects, including Input Delay and cloud connection recovery for Fusion servers.

Forecast Physics

Forecast Physics is one of the main additions in Fusion 2.1.

It provides an alternative to full physics prediction. Instead of fully simulating predicted physics with resimulation, Forecast Physics uses extrapolation to place physics objects in the local time of each player.

The goal is to support real-time physical interaction with Shared Authority while significantly lowering CPU cost compared to full physics prediction.

This is useful for games that need networked physics but do not necessarily require the precision of a fully predicted physics simulation. It is also supported in Shared Authority, making it relevant for serverless multiplayer architectures.

Typical use cases include:

• physics-based co-op interactions
• shared world objects
• vehicles or moving objects with limited authority requirements
• lightweight physical interactions in Shared Mode
• Mobile, XR or CPU-constrained multiplayer games

Forecast Physics does not remove the need to design authority and synchronization carefully. It gives developers another option between simple state sync and full physics prediction.

Object Priority

Fusion 2.1 introduces Object Priority, which gives developers control over how frequently specific networked objects are updated.

Not every object in a session needs the same update rate. Some objects are gameplay-critical and need frequent updates. Others may be distant, inactive, hidden, or less relevant to a specific player.

Object Priority allows developers to adjust update behavior based on game logic.

For example, an object’s priority can be changed depending on:

• distance to the player
• visibility
• gameplay relevance
• interaction state
• team ownership
• whether the object is currently active or idle

This gives teams more control over bandwidth usage and replication cost, especially in sessions with many networked objects.

Configurable Shared Mode Tickrate and Send Rate

Shared Mode now supports configurable tickrate and send rate up to 32 Hz.

This gives developers more control over the trade-off between responsiveness, bandwidth, and CPU usage. Higher rates can improve responsiveness for some game types, while lower rates may be more appropriate for mobile, social, or less latency-sensitive games.

Fusion 2.1 also adds more options for configuring tickrate through the dashboard and webhooks.

Input Delay for Client Host and Dedicated Server

Fusion 2.1 adds Input Delay for Client Host and Dedicated Server topologies.

Input Delay can reduce the number of resimulations clients perform. This can lower CPU cost and reduce the impact of frequent prediction corrections, depending on the game and network conditions.

This is a tuning feature. It introduces a trade-off between responsiveness and simulation stability, so the correct configuration depends on the project.

It is most relevant for games where client resimulation cost is significant and where a small amount of input delay is acceptable.

Large Data RPCs

Fusion 2.1 adds support for Large Data RPCs.

This allows projects to send larger data payloads over RPCs when needed. It is intended for cases where the standard RPC payload size is not sufficient.

Potential use cases include:

• transferring larger custom payloads
• one-off session data messages
• custom initialization flows
• editor or tool-driven multiplayer workflows

Large Data RPCs should still be used deliberately. Sending large payloads too often can affect bandwidth and session performance. For frequent state updates, Networked Properties are the better fit.

PlayerUniqueId

Fusion 2.1 introduces PlayerUniqueId, which allows players to reconnect using a consistent PlayerRef.

This improves reconnect handling for games where player identity inside a session needs to remain stable across disconnects and reconnects.

Improved Master Client Switching

Fusion 2.1 improves Master Client switching behavior.

When the Master Client disconnects, Fusion can switch to a new Master Client without waiting for a full connection timeout.

This reduces disruption in Shared Mode sessions where the Master Client may leave, crash, lose network connectivity, or be backgrounded.

For security reasons master client switching does not happen automatically when the master client becomes unresponsive. Clients can manually request a master client reassignment in case the master client becomes unresponsive but does not fully disconnect.

Server Mode Cloud Connection Recovery

Fusion 2.1 also improves Server Mode cloud connection behavior.

Fusion servers can now move to a new cloud session room after connection loss. This helps keep the session alive if the server loses its connection to the cloud session room.

This is relevant for server-based architectures with longer running sessions.

Updated Fusion 2.1 Samples

Several Fusion samples are already available for Fusion 2.1. More samples will be updated in the following weeks.

Available samples include:

• Fusion Starter
  Beginner examples, including a third-person character, platformer, and shooter.
• Fusion Essentials
  Self-contained examples of core Fusion features.
• Asteroids Advanced
  A top-down arcade shooter with host migration and lag compensation.
• Projectile Essentials
  Five examples for networking projectiles in Fusion.
• Pirate Adventure
  A top-down multiplayer co-op RPG sample.

A Shared Authority MMO Sample is also planned. It will demonstrate several of the new Fusion 2.1 capabilities in a larger Shared Mode context.

Upgrading from Fusion 2.0

Projects using Fusion 2.0 can upgrade to Fusion 2.1 by replacing the SDK and following the update steps in the documentation.

Before upgrading, make sure the project is already on the latest Fusion 2.0.x SDK.

Fusion 2.1 includes only minor breaking API changes, and most upgrades from current Fusion 2.0.x versions should be relatively small.

Read the SDK update instructions

For new projects, Fusion 2.1 is the recommended version.

Fusion 2.0 remains supported with bug fixes. Fusion 2.0 and Fusion 1 projects continue to run on Photon Cloud without required changes.

Summary

Fusion 2.1 Stable adds several features aimed at practical multiplayer production work.

Forecast Physics provides a lower-cost option for networked physics, including Shared Mode support. Object Priority gives developers more control over replication frequency and bandwidth. Configurable Shared Mode tickrate and send rate allow better tuning for different game types and platforms. Input Delay helps reduce resimulation cost in Host and Server Mode. Large Data RPCs, PlayerUniqueId, improved Master Client switching, and Server Mode cloud connection recovery address specific session, reconnect, and data transfer scenarios.

For teams building with Fusion, the release provides more control over synchronization behavior, session stability, and performance trade-offs.

Download Fusion 2.1 Stable
Download Fusion 2.1 Stable from the Unity Asset Store
Read the full Fusion 2.1 release notes