A fast, modern way to play Ultimate Tic-Tac-Toe online — free and open source.
Rust powers the backend ⚡, and Vite + HeroUI power the frontend 🎨

Play now: https://UltimateXO.com

It’s Tic-Tac-Toe played on a 3×3 grid of 3×3 boards (81 squares). Each move sends your opponent to a specific sub-board, creating a mix of local tactics and big-picture strategy.

• Clean, responsive web UI
• Fast Rust engine
• Real-time moves
• Works great on desktop & mobile
• Automated CI/CD
• Fully open source

• Frontend: Vite, React, TypeScript, HeroUI, pnpm
• Backend: Rust, axum, Tokio
• Infra: Docker, Caddy, Cloudflare, GitHub Actions

Requirements: Node 20+, pnpm 8+, Rust 1.75+, Docker (optional)

git clone https://github.com/open-syntax/ultimatexo.git
cd ultimatexo

Install:

just setup
# or:
cd client && pnpm install
cd ../server && cargo build

Run:

just dev
# Client: http://localhost:5173
# Server: http://localhost:6767

just docker-build
just docker-up

1. The board is a 3×3 grid of smaller boards
2. X starts anywhere
3. Your move decides where the opponent must play next
4. Win small boards with three-in-a-row
5. Win the game by taking three small boards in a row
6. If a sub-board is finished, you can play anywhere

Contributions welcome! Focus areas: testing, UI, WebSocket reliability, documentation, accessibility.
See CONTRIBUTING.md

See SECURITY.md

AGPLv3

Issues • Discussions • Discord • UltimateXO.com

If you find this useful, Please consider supporting us on Ko-Fi, or just star the repo :)

Ready to play? 🎯