Forge Concept Lifecycle

Mod Lifecycle

During mod loading, lifecycle events fire on the mod-specific event bus. Register listeners via @EventBusSubscriber(bus = Bus.MOD) or in the mod constructor:

@Mod.EventBusSubscriber(modid = "mymod", bus = Mod.EventBusSubscriber.Bus.MOD)
public class MyModEventSubscriber {
  @SubscribeEvent
  static void onCommonSetup(FMLCommonSetupEvent event) { ... }
}

@Mod("mymod")
public class MyMod {
  public MyMod(FMLModLoadingContext context) {
    context.getModEventBus().addListener(this::onCommonSetup);
  }
  private void onCommonSetup(FMLCommonSetupEvent event) { ... }
}

Warning: most lifecycle events fire in parallel — all mods receive the same event concurrently. Mods must be thread-safe; defer work via ParallelDispatchEvent#enqueueWork.

Registry events

Fired synchronously after mod construction, in order:

• NewRegistryEvent: register custom registries via RegistryBuilder.
• DataPackRegistryEvent$NewRegistry: register custom datapack registries by providing a Codec for JSON encode/decode.
• RegisterEvent: fired for each registry to register objects.

Prefer DeferredRegister over registry events where possible — it handles timing and is less error-prone.

Data generation

If data generators run, GatherDataEvent fires last (synchronously) to register data providers.

Common setup

FMLCommonSetupEvent: actions common to client and server (e.g. registering capabilities).

Sided setup

FMLClientSetupEvent (physical client) and FMLDedicatedServerSetupEvent (dedicated server): physical-side initialization such as key bindings.

InterModComms

Cross-mod messages: InterModEnqueueEvent (send via InterModComms#sendTo with mod id, key, and a supplier of data) and InterModProcessEvent (receive via InterModComms#getMessages, optionally filtered by key predicate; returns IMCMessages). Backed by a ConcurrentMap, safe during lifecycle events.

Also: FMLConstructModEvent (after mod construction, before RegisterEvent) and FMLLoadCompleteEvent (after InterModComms, when loading completes).

1.21.11+ mod lifecycle note

In this Forge build, do NOT use context.getModEventBus() or FMLJavaModLoadingContext.get().getModEventBus(). Use FMLJavaModLoadingContext.get().getModBusGroup() and typed event buses. For lifecycle listeners, read the event class's static BUS field or use the typed bus registration shown in the current event API guidance.