world-system-filter

WorldSystemFilter

Intent

Scope a system to specific world types (game world, editor world, thin client, server) so it runs exactly where needed and is excluded from worlds where it would be incorrect or harmful.

Use When

Custom transform systems that must preview correctly in the subscene editor. Systems that are editor-only (tooling, diagnostics). Multi-world architectures (client/server, editor/runtime).

Avoid When

Single-world games with no editor-preview requirements and no multi-world architecture — the default behavior (Default world only) is correct.

Senior Pattern

• [WorldSystemFilter(WorldSystemFilterFlags.Default)] — default world only (implicit, same as omitting the attribute).
• [WorldSystemFilter(WorldSystemFilterFlags.Default | WorldSystemFilterFlags.Editor)] — game world and editor live-baking world.
• [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)] — server world only (Netcode for Entities).
• Flags are OR-combined for multi-world membership.

Code Template

// Custom 2D transform — must work in editor subscene preview:
[BurstCompile]
[WorldSystemFilter(WorldSystemFilterFlags.Default | WorldSystemFilterFlags.Editor)]
[UpdateInGroup(typeof(TransformSystemGroup))]
[UpdateAfter(typeof(ParentSystem))]
public partial struct Transform2DSystem : ISystem
{
    [BurstCompile]
    public void OnUpdate(ref SystemState state) { }
}

// Server-only simulation system:
[BurstCompile]
[WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
[UpdateInGroup(typeof(SimulationSystemGroup))]
public partial struct AuthoritativeMovementSystem : ISystem { }

Anti-Patterns

• Implementing a custom transform or rendering system without the Editor flag — system works in PlayMode but subscene editing preview is broken (entities appear in wrong position/orientation).
• Adding WorldSystemFilter.Editor to a system that reads from external/network state — editor world has no network connection.
• Omitting the attribute entirely when building a server-only system — system runs in the client world too, causing unintended computation.