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Privacy notice
What Lasker keeps, what it sends and to whom, how long it is kept, and the free software it is built on.
Last updated 8 October 2026.
Lasker shows no advertising and uses no advertising or analytics trackers.
Without an account, your games and progress stay in your browser. Only chess positions are sent to be analysed, never anything about you.
Your data is never sold or shared for marketing.
| What | When | Where it goes | How long |
|---|---|---|---|
| Your games, habits, practice, lessons and settings | Always | This browser only | Until you clear it in Settings |
| The same, plus your email address | If you sign in | Your account (Supabase) | While you have an account |
| Positions, engine facts, your typed or spoken questions | Only when you use the AI coach (18+) | Sent to Google Gemini to write the answer | Not stored by Lasker |
| Chess positions (just the pieces on the board) | When Stockfish analyses a game or plays a move | Lasker's engine server, which runs Stockfish | Not stored with anything about you; a short-lived cache of positions |
| The username you type to import games | Only when you use Find my habits | Sent to Chess.com or Lichess to fetch your public games | Remembered in this browser |
| Online and friend games, chat messages | When you play online | Supabase, readable only by the two players | Chat is deleted with its game |
| A recording you upload to read a game | Only when you use the video reader | Our video service | Deleted as soon as it has been read |
| Your IP address, as a counter | Every request to our servers | Our database, to stop abuse | 2 hours (daily totals: 3 days) |
These companies process data for Lasker only to provide the feature named. Each has its own privacy policy.
The AI coach, Think With Me, voice moves and Live talk use Google's Gemini service. Google allows them only for people aged 18 or over, so Lasker asks signed-in players to confirm their age once before using them. Everything else (playing, reviews, challenges, habits, lessons) is open to every age and never uses Gemini.
Stockfish decides what is good or bad in a position; Gemini only puts that into words.
The chess engine is Stockfish, free software under the GNU General Public License v3. Lasker ships the browser build from the stockfish.js package, version 19.0.0, unmodified, and its engine server runs the official Stockfish release, also unmodified. Its source code:
Lasker also uses chess.js (BSD-2-Clause), react-chessboard (MIT), Next.js (MIT), React (MIT) and Lucide icons (ISC). Each keeps its own licence and copyright.
If this notice changes in a way that matters, the banner at the top of the site will ask you to read it again.