SideChess — Play Chess in the Side Panel

Play chess against Stockfish in your side panel. Adjustable strength. Works offline, no signup.

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.