@colyseus/react

React hooks for Colyseus multiplayer applications.

Installation

npm install @colyseus/react

Peer dependencies: @colyseus/sdk, @colyseus/schema, and react (>=18.3.1).

Server-side rendering

Every hook is safe to render on the server. A room is a live client-side connection and is never serialized for hydration, so on the server the hooks render as though nothing is connected — useRoomState() returns undefined, useRoom() reports isConnecting: true, and the predict hooks return undefined. Connection happens in an effect, so the live room arrives on the re-render right after hydration.

Render the connecting state rather than assuming state exists:

const players = useRoomState((state) => state.players);
if (!players) return <Spinner />;   // server render + first client paint

The package ships a "use client" directive, so you can import it from a Next.js App Router Server Component without the build failing. The hooks themselves still run on the client, as any React hook does.

Hooks

useRoom(callback, deps?)

Manages the lifecycle of a Colyseus room connection. Handles connecting, disconnecting on unmount, and reconnecting when dependencies change. Works correctly with React StrictMode.

import { Client } from "@colyseus/sdk";
import { useRoom } from "@colyseus/react";

const client = new Client("ws://localhost:2567");

function Game() {
  const { room, error, isConnecting } = useRoom(
    () => client.joinOrCreate("game_room"),
  );

  if (isConnecting) return <p>Connecting...</p>;
  if (error) return <p>Error: {error.message}</p>;

  return <GameView room={room} />;
}

The first argument is a callback that returns a Promise<Room> — any Colyseus matchmaking method works (joinOrCreate, join, create, joinById, consumeSeatReservation).

Reconnecting on dependency changes:

const { room } = useRoom(
  () => client.joinOrCreate("game_room", { level }),
  [level],
);

When level changes the previous room is left and a new connection is established.

Conditional connection:

Pass a falsy value to skip connecting until a condition is met:

const { room } = useRoom(
  isReady ? () => client.joinOrCreate("game_room") : null,
  [isReady],
);

useRoomState(room, selector?)

Subscribes to Colyseus room state changes and returns immutable plain-object snapshots. Unchanged portions of the state tree keep referential equality between renders, so React components only re-render when the data they use actually changes.

import { useRoom, useRoomState } from "@colyseus/react";

function Game() {
  const { room } = useRoom(() => client.joinOrCreate("game_room"));
  const state = useRoomState(room);

  if (!state) return <p>Waiting for state...</p>;

  return <p>Players: {state.players.size}</p>;
}

Using a selector to subscribe to a subset of the state:

const players = useRoomState(room, (state) => state.players);

Only components that read players will re-render when the players map changes.

useRoomMessage(room, type, callback)

Subscribes to Colyseus room messages. The callback is kept in a ref so it is always up-to-date without re-subscribing. Automatically unsubscribes when the room changes or the component unmounts.

import { useRoom, useRoomMessage } from "@colyseus/react";

function Chat() {
  const { room } = useRoom(() => client.joinOrCreate("game_room"));
  const [messages, setMessages] = useState<string[]>([]);

  useRoomMessage(room, "chat", (message) => {
    setMessages((prev) => [...prev, message]);
  });

  return (
    <ul>
      {messages.map((msg, i) => <li key={i}>{msg}</li>)}
    </ul>
  );
}

Pass "*" as the type to listen to all message types.

useLobbyRoom(callback, deps?)

Connects to a Colyseus Lobby Room and provides a live-updating list of available rooms. The list is automatically maintained as rooms are created, updated, and removed.

import { Client } from "@colyseus/sdk";
import { useLobbyRoom } from "@colyseus/react";

const client = new Client("ws://localhost:2567");

function Lobby() {
  const { rooms, error, isConnecting } = useLobbyRoom(
    () => client.joinOrCreate("lobby"),
  );

  if (isConnecting) return <p>Connecting...</p>;
  if (error) return <p>Error: {error.message}</p>;

  return (
    <ul>
      {rooms.map((room) => (
        <li key={room.roomId}>
          {room.name} — {room.clients}/{room.maxClients} players
        </li>
      ))}
    </ul>
  );
}

Return value:

useQueueRoom(connect, consume, deps?)

Manages the full lifecycle of a Colyseus matchmaking queue: connecting to the queue room, tracking group size, receiving a seat reservation, confirming, and consuming the seat to join the match room. Cleans up both rooms on unmount.

import { Client } from "@colyseus/sdk";
import { useQueueRoom } from "@colyseus/react";

const client = new Client("ws://localhost:2567");

function Matchmaking() {
  const { room, clients, isWaiting, error } = useQueueRoom(
    () => client.joinOrCreate("queue", { rank: 1200 }),
    (reservation) => client.consumeSeatReservation(reservation),
  );

  if (error) return <p>Error: {error.message}</p>;
  if (room) return <GameScreen room={room} />;
  if (isWaiting) return <p>Waiting for match... {clients} players in group</p>;
  return <p>Connecting...</p>;
}

The first argument connects to the queue room. The second argument is called with the SeatReservation once a match is found — use client.consumeSeatReservation() to join the match room.

Return value:

Netcode hooks (Colyseus 0.18+)

React bindings for the @colyseus/sdk Predict tools — client prediction, reconciliation and remote smoothing. See the netcode docs for the underlying concepts.

The one rule: structure renders through snapshots, motion renders through predict reads. useRoomState re-renders at patch rate with raw synced values — rendering positions from it gives you jittery patch-rate motion. Predicted/smoothed values change every frame and must stay out of the React render cycle: read them with predict.value(instance, field) inside your frame loop (R3F useFrame, or the usePredictLoop callback) and write into refs.

All hooks below exist in two forms: standalone (useX(room, ...)) and bound (returned by createRoomContext(options), no room argument). Pass Predict options once via createRoomContext({ predict: { mode: "lerp", delay: 100 } }).

usePredict(room, options?)

Returns the room's shared Predict instance. Predict.get() constructs a fresh instance per call, so the hook memoizes one per room, reference-counts consumers, and disposes it when the last consumer unmounts.

useInput(room, options?)

Returns the room's InputHandle (room.input() — idempotent, stable per room). Stage fields on input.data, then input.send() once per fixed step inside the usePredictLoop callback.

usePredictLoop(room, onSteps, options?)

Owns the per-frame driver: calls predict.tick(now) once per frame and hands you the number of fixed steps due — stage + send exactly that many inputs inside the callback ("send before you read"). By default it runs its own requestAnimationFrame; with { external: true } it returns a drive(now?) function to call from a frame loop you already have:

// React Three Fiber — drive at an early priority so ticks precede reads:
const drive = usePredictLoop(onSteps, { external: true });
useFrame(() => drive(), -1);

useReconciler(room, select, options)

Active prediction for the entity you control — predict.reconciler() with the lifecycle handled: waits for the entity to spawn (select: (state, room) => instance), recreates the controller if the server replaces the instance, and disposes on unmount. options.input defaults to the room's handle.

const me = useReconciler(
  (state, room) => state.players.get(room.sessionId),
  { step: (ctx, p, cmd) => applyInput(p, cmd, ctx.dt), smoothing: 15, snap: 5 },
);

useAttachAll(room, key, config, deps?)

Passive smoothing for a root-state collection — predict.attachAll() as an effect, detached on unmount. Attach angular fields in a separate call:

useAttachAll("players", { mode: "lerp", fields: ["x", "y", "z"] });
useAttachAll("players", { mode: "lerp", fields: ["heading"], angle: true });

useEventChannel(room, options)

Optimistic event channel — predict.defineEvent() with teardown on unmount, plus reactivity: the calling component re-renders on predict/confirm/reject/unpredicted, so flag-shaped derives work in plain render code:

const pickups = useEventChannel({
  confirmOn: { collection: "items", field: "alive", equals: false },
});
const hidden = !item.alive || pickups?.has(id);

useEntityInstance(room, select) / useSessionEntity(room, collectionKey)

Select a decoded schema instance (what the Predict APIs key off), re-rendering only when its identity changes — never on field updates. useSessionEntity is the common case: your own entity by sessionId.

getSchemaInstance(snapshot)

Bridges useRoomState snapshots back to their decoded instance, for predict.value() reads on entities you render from snapshot lists:

const source = getSchemaInstance(playerSnapshot);
useFrame(() => { ref.current.position.x = predict.value(source, "x"); });

useInputBuffer()

The "buffer, then consume" input recipe as a hook: press() in the React event handler, consume() inside the send loop so a tap lands on exactly one fixed step — never lost on a 0-step frame, never doubled on a multi-step frame.

For a complete working example (R3F + prediction + remote lerp), see r3f-lobby-car-prototype.

Contexts

createRoomContext()

Creates a set of hooks and a RoomProvider component that share a single room connection across React reconciler boundaries (e.g. DOM + React Three Fiber). The room is stored in a closure-scoped external store rather than React Context, so the hooks work in any reconciler tree that imports them.

import { Client } from "@colyseus/sdk";
import { createRoomContext } from "@colyseus/react";

const client = new Client("ws://localhost:2567");

const { RoomProvider, useRoom, useRoomState } = createRoomContext();

Wrap your app with RoomProvider:

function App() {
  return (
    <RoomProvider connect={() => client.joinOrCreate("game_room")}>
      <UI />
      <Canvas>
        <GameScene />
      </Canvas>
    </RoomProvider>
  );
}

RoomProvider accepts a connect callback (same as the standalone useRoom hook) and an optional deps array. Pass a falsy value to connect to defer the connection.

Use the hooks in any component — DOM or R3F:

function UI() {
  const { room, error, isConnecting } = useRoom();
  const players = useRoomState((state) => state.players);

  if (isConnecting) return <p>Connecting...</p>;
  if (error) return <p>Error: {error.message}</p>;

  return <p>Players: {players?.size}</p>;
}

The returned useRoom() and useRoomState(selector?) work identically to the standalone hooks but don't require you to pass the room as an argument.

createLobbyContext()

Creates a LobbyProvider and useLobby hook for sharing lobby room data globally across your app — useful when you need room metadata available persistently alongside an active game room, not just on a lobby screen. Like createRoomContext, it uses a closure-scoped external store so the hook works across reconciler boundaries.

import { Client } from "@colyseus/sdk";
import { createLobbyContext, createRoomContext } from "@colyseus/react";

const client = new Client("ws://localhost:2567");

const { LobbyProvider, useLobby } = createLobbyContext<MyMetadata>();
const { RoomProvider, useRoom, useRoomState } = createRoomContext();

Wrap your app with LobbyProvider (can nest with RoomProvider):

function App() {
  return (
    <LobbyProvider connect={() => client.joinOrCreate("lobby")}>
      <RoomProvider connect={() => client.joinOrCreate("game_room")}>
        <UI />
        <Canvas>
          <GameScene />
        </Canvas>
      </RoomProvider>
    </LobbyProvider>
  );
}

LobbyProvider accepts a connect callback (same as useLobbyRoom) and an optional deps array. The lobby connection persists independently of the game room.

Access lobby data from any component — even deep inside the game:

function RoomBrowser() {
  const { rooms, error, isConnecting } = useLobby();

  if (isConnecting) return <p>Loading rooms...</p>;
  if (error) return <p>Error: {error.message}</p>;

  return (
    <ul>
      {rooms.map((room) => (
        <li key={room.roomId}>
          {room.metadata.displayName} — {room.clients}/{room.maxClients}
        </li>
      ))}
    </ul>
  );
}

The returned useLobby() hook provides the same fields as useLobbyRoom (rooms, room, error, isConnecting).

Credits

Inspiration and previous work by @pedr0fontoura — use-colyseus. Rewrite and new useRoomState() made by @FTWinston.