Privacy Policy

Last updated: July 2, 2026

Chesslinebook (chesslinebook.com and the Chesslinebook mobile apps) is a chess opening notebook and trainer. This page explains what information the app handles and what happens to it. The short version: we collect the minimum needed to make the app work, we show no ads, we use no tracking, and we never sell your data.

What we collect

Email address — only if you choose to sign in. It is used to send you a one-time login code and to identify your account. Signing in is optional; the app works without an account.
Content you create — your notebooks (chess lines, comments, notes) and appearance preferences are stored in your account when you are signed in, so they can sync across your devices.

Stored only on your device: if you use Chesslinebook without signing in, your notebooks live in your browser's local storage and never leave your device. Practice and review progress (spaced-repetition data) is always device-local and is not uploaded, even when signed in.

What we don't do

No advertising and no ad networks
No analytics or tracking scripts
No selling or sharing of personal data with data brokers
No collection of location, contacts, photos, or anything beyond the list above

Sharing you choose to set up

If you add an instructor's email address (or a student shares a notebook with you), that person can see the shared notebooks and leave comments. Comments carry the author's email address so you both know who wrote what. This happens only when you explicitly set it up, and you can remove instructors at any time in Settings.

Services we rely on

Supabase — hosts our database and sign-in system. Your email and synced notebooks are stored there.
Brevo — delivers the login-code emails.
Vercel — hosts the website.

Features that talk to chess services

Some features fetch data directly from third-party chess platforms, only when you use them:

Lichess — position analysis, opening-explorer statistics, and (if you enter your Lichess username) your recent games.
Chess.com — your recent games, if you enter your Chess.com username.

Requests to these services include the position being analyzed or the username you typed, and are subject to their own privacy policies. We send them nothing else.

Deleting your data

You can delete any notebook, comment, or instructor relationship in the app at any time.
To delete your account and everything associated with it, email us at the address below and we will remove it.

Children

Chesslinebook is a general-audience chess study tool. It shows no ads, has no social feed, and collects nothing beyond the items listed above.

Class accounts: a student joining a coach's class with a class code gets an anonymous account — no email address, no password, no personal information beyond the first name (or nickname) they type, which is shown only to their coach. Class-account study data is the same as any account's (notebooks, review progress, puzzles) and can be deleted on request by the coach or a parent via the contact address below.

Changes

If this policy changes, we will update this page and the date at the top.

Contact

Questions or deletion requests: chesslinebookteam@gmail.com. To delete your account and all its data, see Delete your account.