Privacy

Chess Strategy is free, open-source software with no ads and no tracking across sites; it only counts its own use, anonymously (below).

Without logging in

Everything stays in your browser: your scores, your games and their analysis. If you add a Chess.com username, our server fetches that player's public games from Chess.com for you, and keeps nothing.

When you log in with Lichess

Lichess tells us your username and nothing else: never your password or email. We keep, in your account:

your Lichess username;
your training: which positions you played, when, and your score;
your last 100 games from Lichess and Chess.com, synced automatically (moves, ratings, time control, date, and Lichess's or our engine's evaluations);
if you add it, your Chess.com username (your public Chess.com games are read through our server).

Your Lichess login stays in your browser. Our server keeps only a fingerprint of it, for a day, so it doesn't ask Lichess again on every request. Logging out removes it, and cancels our access on Lichess.

When you log in with Google

Google tells us your email address and an id for your Google account, nothing else: never your password, and no access to your Google account, mail or files. We keep the email address in your account to show which account you're in, and the same things as above (your training, your games, your Chess.com username if you add it). We never write to you. Your login stays in your browser; our server keeps only a fingerprint of it. Logging out removes it.

Where it is kept

On Cloudflare's servers, which run our account server and its database, and in your browser. We don't share or sell anything, and we use no outside analytics or advertising services.

Usage counts

To see what works and what to improve, the website counts anonymously how it is used: visits, positions played (which exercise, the score, master or own game, in the daily routine or not), how many positions are found in your games, and for each device its language, how you're logged in (not at all, Lichess or Google), whether a Chess.com username is added, whether it runs as the installed app, and whether the chess engine failed to load. These counts carry a random number kept in your browser, never your name, username or account, and are deleted after 13 months. No other site is involved.

Donations

The Support page shows Ko-fi's button, loaded from Ko-fi. Donations are handled by Ko-fi under its own privacy policy. Ko-fi tells us what you choose to share with a donation (such as your name or a message); it is not linked to your account here.

Deleting your data

In the app: Profile › Delete my account. Everything above is deleted at once, for good. To remove only your Chess.com games, disconnect Chess.com in your profile.

Questions

Open an issue on GitHub. The code that does all of this is there too.