Manual

The interface reference says what every function does. These pages say what to reach for and why, which the signatures cannot.

If this is your first mod

Read Realms and the session lifecycle first — everything else assumes you know which realm your code runs in. Then read What you cannot build yet: it is short, and it will save you more time than any other page here.

Getting your bearings

Realms and the session lifecycleServer realm, client realm, and what happens between a session starting and ending.

Choosing a languageA mod is a WebAssembly component. What that does and does not let you write it in.

What you cannot build yetThe honest list. Read it before planning anything ambitious.

LimitsThe ceilings the host enforces, and what happens when you reach one.

Shipping content

Addons and identityHow content is laid out on disk and how its name is derived from where it sits.

The mod manifestWhat a mod declares about itself.

ArchetypesPublishing a thing that can exist in the world.

ComponentsThe accessible surface of an entity: what you may read and write.

Acting on the world

Entities and controlSpawn, despawn, possess and release. A body is a role, not a type.

InteractionBeing pressed: reach, aim and who resolves the hit.

Contact eventsPhysical touch, folded into events you can act on.

Spatial queriesRaycasts and overlaps, and what they deliberately do not return.

Talking to other code

SignalsMod-to-mod events over a host-routed bus, with an unforgeable source.

Broadcast and RPCReaching the client half of your own mod, and answering it.

GamemodesThe one role a session designates, and what it is allowed to own.