CAPYBARAStart free
A vibrant AI-generated floating-island game world

Free tools for your next AI game

You made a game with AI. We make it playable — auth, multiplayer, saves, analytics, and shareable links in one small SDK.

Start building freeSee how it works

Free for now · No backend setup · No credit card

From AI prototype to playable game

Your agent can build the game logic. We handle the layer that makes it usable by real players.

1

Prompt your game

Your agent builds the gameplay.

2

Add the SDK

One file, one game ID.

3

Share a link

A playable URL for anyone.

4

Play together

Guests, saves, multiplayer.

Everything your game needs after it starts working

Game world with a shareable link bar and a link-copied toast
capybara.build/g/island-run-42
Link copied — send it to a friend

Shareable URL

Ship a playable link in seconds

Your game shouldn't live only on localhost. Add the SDK and get a shareable URL you can send to anyone.

capybara.build/g/island-run-42

Free to share. Free to test. Free to show your friends.

Three players together in the game world with presence tags
AdaJunguest-3
Same session · room “lobby”

Multiplayer

Tell your agent to make it multiplayer

Rooms, player presence, and shared state — without building your own networking stack.

“Add 4-player multiplayer: create a room and sync player positions.”
Player overlooking the game world with a progress-restored toast
Progress restored · level 7

Saves

Let players pick up where they left off

Progress, inventory, and unlocks in one JSON document per player — so a prototype feels like a real game.

await sdk.save.saveGameData({ level: 7, coins: 1200 })
Game world with a continue-as-guest sign-in card

Continue as guest?

Play instantly — no password needed.

Play as guest

Player identity

Give every player an identity

Guest sign-in and email accounts, tied to saves and multiplayer sessions. No passwords in your game.

await sdk.auth.loginAsGuest()
Game world with a weekly player activity chart overlay
12 players this week

Sessions this week

1,284

+18%
MTWTFSS

Analytics

See how people actually play

Sessions, playtime, and players, tracked automatically. No pipeline to wire, no dashboard to build.

Open your dashboard and watch the first play session land.

Made for prompting, not plumbing

Your coding agent can already build gameplay. Give it the SDK and ask for the rest.

“Add guest auth to my game”
“Make this game multiplayer”
“Save the player inventory”
“Track when players finish level 1”

// paste the brief, then prompt

import { sdk } from "./sdk"

sdk.init()

await sdk.auth.loginAsGuest()

await sdk.multiplayer.joinRoom("lobby")

Everything here is free

Build weird things. Test ideas fast. Share prototypes freely.

  • Free SDK
  • Free auth
  • Free multiplayer
  • Free save system
  • Free analytics
  • Free shareable URLs

No credit card · No backend setup

Your AI can build the game. We help it ship.

Add auth, multiplayer, saves, analytics, and instant links — free.

Start free