PartyKit Has a Free API: Build Real-Time Multiplayer Apps With Cloudflare Durable Objects

#partykit #realtime #cloudflare #webdev

WebSockets are easy to start, impossible to scale. PartyKit makes multiplayer real-time apps deployable with one command.

What Is PartyKit?

PartyKit is a platform for building real-time, multiplayer, collaborative applications. It runs on Cloudflare's network using Durable Objects for stateful server logic.

// party/main.ts — server logic
import type { Party, Connection } from "partykit/server"

export default class ChatRoom implements Party.Server {
  messages: string[] = []

  onConnect(conn: Connection) {
    // Send message history to new connections
    conn.send(JSON.stringify({ type: "history", messages: this.messages }))
  }

  onMessage(message: string, sender: Connection) {
    this.messages.push(message)
    // Broadcast to ALL connections in this room
    this.room.broadcast(JSON.stringify({ type: "message", text: message }))
  }
}

npx partykit dev   # Local dev
npx partykit deploy  # Deploy globally

Client

import PartySocket from "partysocket"

const ws = new PartySocket({
  host: "my-app.username.partykit.dev",
  room: "chat-room-1",
})

ws.addEventListener("message", (e) => {
  const data = JSON.parse(e.data)
  console.log(data)
})

ws.send("Hello everyone!")

Use Cases

Multiplayer games — shared game state across players
Collaborative editing — Google Docs-like real-time editing
Live dashboards — real-time metrics visible to all viewers
Chat — rooms, presence, typing indicators
Voting/polling — instant results across all clients

Why PartyKit

Rooms — each room is an isolated Durable Object with its own state
Global — runs on Cloudflare's 300+ edge locations
Stateful server — not just pub/sub, actual server-side logic per room
Hibernation — rooms sleep when empty, wake on first connection ($0 when idle)
Yjs integration — CRDT-based collaborative editing built in