Sidechess — Play Chess In

SideChess turns your Chrome side panel into a quiet chess board you can
play whenever you have a minute.

— Real Stockfish 18 engine inside. Strength scales from absolute beginner
(~600 Elo) to full grandmaster level (3000+ Elo).
— Two simple sliders: how long the engine should think, and how strong
it should play. That's the entire setup.
— Make a move, switch tabs, come back later. Your game is saved
automatically.
— Works completely offline. No accounts. No tracking. No internet
needed after install.
— Light and dark themes.

Perfect for slow correspondence-style games during the workday, when
you don't want to commit to a 10-minute blitz on a chess website.

The engine uses Stockfish (GPL-3) and chess pieces by Cburnett (CC BY-SA 3.0).
Open source — see GitHub link in support page.