Last updated: April 8, 2026
Backrank ("we", "us") is a chess training app that helps you learn from your blunders using spaced repetition. This policy explains what data we collect, how we use it, and who we share it with.
Account information. When you sign up, we store your email address and a hashed password (or Google account identifier if you use Google Sign-In). We also store your chess.com username, which you provide during onboarding.
Chess data. We fetch your publicly available game history from the Chess.com API using your username. We analyze positions locally in your browser using the Stockfish engine and store training cards derived from your games. Each card contains: the board position (FEN), the best move, the move you played, engine evaluations, your opponent's username, game date, and time control.
Practice data. We track your quiz sessions including date, number of cards reviewed, accuracy, and duration. This is used to calculate streaks, display statistics, and schedule future reviews via spaced repetition.
Settings and preferences. Your app settings (theme, daily card limits, board appearance, etc.) are stored in your profile.
Payment information. If you subscribe to Backrank Pro, payment is processed entirely by Stripe. We never see or store your credit card number. We store only your Stripe customer ID and subscription status to manage your plan.
We use the following services to operate Backrank:
Supabase provides our database, authentication, and backend infrastructure. Your account data, cards, and session history are stored in Supabase's cloud infrastructure.
Stripe processes all payments. When you subscribe to Pro, you are redirected to Stripe's hosted checkout page. Stripe handles your payment details under their own privacy policy. We only receive your subscription status and Stripe customer ID.
Chess.com API is used to fetch your publicly available game history. We send only your chess.com username, which is public information. No authentication credentials for Chess.com are required or collected.
Google is available as an authentication option. If you sign in with Google, we receive your email and basic profile information through standard OAuth. We do not access any other Google data.
Cloudflare Turnstile is used during account creation to verify you are a real person. It does not use cookies or track you across sites.
Vercel Analytics collects anonymous, aggregated page view and performance data to help us monitor app health. No personally identifiable information is included.
Game analysis is performed entirely in your browser using the Stockfish chess engine (WebAssembly). Your game positions are not sent to any server for analysis.
If you use Backrank without creating an account, all data is stored in your browser's local storage and never leaves your device.
All data in transit is encrypted via HTTPS. Our database uses row-level security policies so that each user can only access their own data. Passwords are hashed by Supabase's authentication system and are never stored in plain text.
Your data is retained for as long as you have an active account. You can delete your account and all associated data by contacting us. Upon deletion, we remove your profile, cards, session history, and cancel any active subscription.
Backrank is not directed at children under 13. We do not knowingly collect data from children under 13. If you believe a child has provided us data, please contact us and we will delete it.
We may update this policy from time to time. If we make material changes, we will notify you through the app. The "last updated" date at the top reflects the most recent revision.
If you have questions about this policy or want to request data deletion, contact us at gavinniendorf [at] gmail [dot] com.
Backrank · backrank.io