About 4sly.io

4sly.io is a fast, modern chess arena built for head-to-head play, pass-and-play, and AI showdowns.

How it works

Choose a time control, pick a mode, and start a game instantly. Link mode shares one board across two devices, while Play mode keeps everything on a single screen.

AGI mode

Challenge our strongest engine models in AGI mode with usage-based billing and clear time controls.

Built for focus

Minimal UI, sharp clocks, and fast rematches keep the game moving.

Contact

Questions or feedback? Email support@4sly.io.