Multiplayer for web games: The Gang's All Here!

Lobbies, parties, chat, leaderboards and webhooks, without writing a server. Paste a few lines, get multiplayer.

Ping(you → relay)

100ms

SDK: ~20KB GZ
FREE TIER: —
SETUP: 5 MIN

room codes · invite links · desync at tick 4096 · scale to two regions · profanity filter · certbot renew · 404 lobby not found · rollback netcode · authoritative server · write a lobby server · invite links · room codes ·

scale to two regions · desync at tick 4096 · both players left? · desync at tick 4096 · kubectl apply -f · store high scores · port forward 7777 · presence · certbot renew · rollback netcode · 404 lobby not found · redis pub/sub ·

rate limit chat · NAT punch-through · authoritative server · webhook signatures · webhook signatures · webhook signatures · TODO: reconnect logic · sticky sessions · ping spikes · NAT punch-through · webhook signatures · anti-cheat ·

redis pub/sub · socket.on('close') · presence · ws://localhost:8080 · sticky sessions · store high scores · rate limit chat · invite links · load balancer · ws://localhost:8080 · rate limit chat · anti-cheat ·

retry with backoff · TODO: reconnect logic · fix it in prod · load balancer · anti-cheat · certbot renew · who is host now? · sticky sessions · ping spikes · store high scores · matchmaking queue · profanity filter ·

write a lobby server · ping spikes · leaderboard pagination · room codes · desync at tick 4096 · anti-cheat · rate limit chat · sticky sessions · rollback netcode · presence · who is host now? · presence ·

matchmaking queue · ws://localhost:8080 · matchmaking queue · leaderboard pagination · kubectl apply -f · both players left? · certbot renew · rate limit chat · authoritative server · desync at tick 4096 · store high scores · store high scores ·

presence · kubectl apply -f · anti-cheat · fix it in prod · who is host now? · redis pub/sub · leaderboard pagination · who is host now? · fix it in prod · matchmaking queue · load balancer · invite links ·

404 lobby not found · NAT punch-through · redis pub/sub · npm i socket.io · fix it in prod · invite links · room codes · works on my machine · authoritative server · webhook signatures · store high scores · who is host now? ·

write a lobby server · jitter buffer · save slots · works on my machine · who is host now? · who is host now? · rate limit chat · presence · retry with backoff · rollback netcode · redis pub/sub · works on my machine ·

ws://localhost:8080 · store high scores · redis pub/sub · both players left? · jitter buffer · socket.on('close') · who is host now? · NAT punch-through · ws://localhost:8080 · TODO: reconnect logic · NAT punch-through · certbot renew ·

presence · save slots · jitter buffer · both players left? · redis pub/sub · NAT punch-through · NAT punch-through · authoritative server · presence · write a lobby server · sticky sessions · fix it in prod ·

rollback netcode · save slots · redis pub/sub · webhook signatures · presence · store high scores · npm i socket.io · authoritative server · both players left? · load balancer · store high scores · authoritative server ·

heartbeat timeout 30s · store high scores · matchmaking queue · both players left? · ping spikes · authoritative server · rate limit chat · kubectl apply -f · ping spikes · 404 lobby not found · desync at tick 4096 · leaderboard pagination ·

works on my machine · kubectl apply -f · authoritative server · ws://localhost:8080 · anti-cheat · port forward 7777 · TODO: reconnect logic · heartbeat timeout 30s · invite links · TODO: reconnect logic · scale to two regions · scale to two regions ·

ping spikes · profanity filter · TODO: reconnect logic · certbot renew · rate limit chat · anti-cheat · kubectl apply -f · TODO: reconnect logic · authoritative server · socket.on('close') · port forward 7777 · certbot renew ·

load balancer · invite links · jitter buffer · 404 lobby not found · heartbeat timeout 30s · retry with backoff · socket.on('close') · npm i socket.io · profanity filter · kubectl apply -f · desync at tick 4096 · both players left? ·

rollback netcode · certbot renew · jitter buffer · both players left? · webhook signatures · 404 lobby not found · save slots · rate limit chat · store high scores · npm i socket.io · profanity filter · desync at tick 4096 ·

redis pub/sub · invite links · socket.on('close') · rollback netcode · redis pub/sub · kubectl apply -f · who is host now? · fix it in prod · rollback netcode · npm i socket.io · kubectl apply -f · kubectl apply -f ·

profanity filter · ws://localhost:8080 · redis pub/sub · jitter buffer · leaderboard pagination · jitter buffer · port forward 7777 · both players left? · redis pub/sub · works on my machine · write a lobby server · write a lobby server ·

desync at tick 4096 · 404 lobby not found · rate limit chat · leaderboard pagination · port forward 7777 · kubectl apply -f · works on my machine · socket.on('close') · room codes · fix it in prod · write a lobby server · NAT punch-through ·

kubectl apply -f · both players left? · invite links · load balancer · save slots · save slots · who is host now? · load balancer · kubectl apply -f · authoritative server · store high scores · works on my machine ·

jitter buffer · who is host now? · 404 lobby not found · socket.on('close') · ping spikes · ping spikes · matchmaking queue · 404 lobby not found · authoritative server · scale to two regions · leaderboard pagination · heartbeat timeout 30s ·

ping spikes · works on my machine · load balancer · room codes · jitter buffer · ws://localhost:8080 · invite links · room codes · load balancer · authoritative server · presence · ping spikes ·

npm i socket.io · NAT punch-through · leaderboard pagination · port forward 7777 · NAT punch-through · ping spikes · matchmaking queue · sticky sessions · 404 lobby not found · port forward 7777 · room codes · presence ·

room codes · room codes · socket.on('close') · 404 lobby not found · webhook signatures · ws://localhost:8080 · sticky sessions · load balancer · authoritative server · leaderboard pagination · webhook signatures · who is host now? ·

load balancer · load balancer · jitter buffer · load balancer · save slots · save slots · redis pub/sub · rollback netcode · webhook signatures · store high scores · heartbeat timeout 30s · desync at tick 4096 ·

leaderboard pagination · both players left? · room codes · ws://localhost:8080 · works on my machine · jitter buffer · matchmaking queue · write a lobby server · heartbeat timeout 30s · write a lobby server · jitter buffer · port forward 7777 ·

anti-cheat · anti-cheat · rate limit chat · sticky sessions · ping spikes · fix it in prod · rollback netcode · profanity filter · save slots · desync at tick 4096 · ping spikes · webhook signatures ·

heartbeat timeout 30s · leaderboard pagination · desync at tick 4096 · invite links · both players left? · room codes · redis pub/sub · redis pub/sub · profanity filter · certbot renew · heartbeat timeout 30s · both players left? ·

Multiplayer Simplified.

Lobbies
Quick match, room codes or a server browser. The host can kick, lock and name the room.
relay.quickMatch()
Parties
Invite codes. Friends queue together and land in the same room.
relay.createParty()
Netcode
Declare what moves and who owns it. The SDK syncs and smooths it, and a new host carries on if one drops.
room.define()
Chat
Room chat with names and avatars. Short, safe, rate limited.
room.chat('gg')
Leaderboards
High score boards for every game. Submit a score, show the top ten.
leaderboard.submit()
Saves
Key-value storage per player. Progress that sticks.
storage.set()
Webhooks
Signed events to your backend when players join, score and chat.
POST → your backend
Moderation
Kick players or close rooms from the dashboard, MCP or your backend, with event logs for every game.
kick · close · logs
Persistence
Rooms are snapshotted and players reconnect to the same seat.
on('player_reconnected')

Built for AI coding agents

Let your AI wire it up.

The whole integration guide lives in one plain-text file written for LLMs. Point your agent at it, or connect the MCP server so it can pull the guide and a starter game on its own. Sign it in to your account and it can create instances, change settings, read logs, moderate rooms and wire up webhooks too.

Prompt

llms.txt

Add online multiplayer to my game with GameRelay. Read https://gamerelay.io/llms.txt first and follow it.

MCP server

docs · or your account

Manage your account too (opens your browser to approve, once):

Other clients (Cursor, Windsurf, Claude Desktop):

{
  "mcpServers": {
    "gamerelay": {
      "type": "http",
      "url": "https://gamerelay.io/mcp"
    },
    "gamerelay-account": {
      "type": "http",
      "url": "https://gamerelay.io/mcp/admin"
    }
  }
}

SendRelayReceive.

LVL 1
Make an account
Free. Spin up an instance for each game you ship.
LVL 2
Grab your key
Add one script tag and paste your public key into your game.
LVL 3
Go multiplayer
Join a room and declare what moves. We handle syncing, host changes, reconnects and saves.

GAME.JS

const relay = await GameRelay.connect({
  publicKey: "gr_pub_8f2k…",
});
const room = await relay.quickMatch();

const ships = room.define("ship", { x: "number", y: "number" });
const me = ships.spawn({ x, y });
me.x += 5; // synced and smoothed for everyone
relay.storage.set("highscore", score);█

PLAYER 2 HAS ENTERED

Ship multiplayer tonight.

Create free account

Select your plan

Priced like a coffee.

Limits are per account, across all your games. Every plan gets every core feature. GameRelay is in alpha, so prices and limits may change before launch.

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Multiplayer for web games: Multiplayer for web games▌The Gang's All Here!

Ping(you → relay)

Multiplayer Simplified.[NETCODE]

Lobbies

Parties

Netcode

Chat

Leaderboards

Saves

Webhooks

Moderation

Persistence