Last updated May 2026.
This policy explains what information Mainline collects, how we use it, and the choices you have. Mainline is a chess-training application.
When you create an account, our authentication provider collects your name and email address from the sign-in method you choose (Google, Apple, or email and password).
If you connect a chess platform, we store the chess.com or lichess username you provide so we can read your public games for analysis.
As you train, we store your games, the analysis results, and your learning progress.
If you subscribe, we store your subscription status. Payment card details are handled entirely by our payment provider and are never stored by Mainline.
We also process basic usage and device information needed to run the application.
We use your information to provide and personalize your training, analyze the games you choose to import, process and manage your subscription, keep your account secure, and improve the product.
Your training progress is stored on your device in the browser. When you are signed in, it is also synced to our database so it follows your account across devices. You can export a full backup of your local data at any time from Settings.
We share the minimum data necessary with the providers that run Mainline: our authentication provider (account and session), our payment providers Stripe and RevenueCat (subscription billing), our database and application hosting providers, and chess.com and lichess (we read your public games through their APIs only when you connect an account). Each provider processes data under its own terms.
We use only the essential cookies required to keep you signed in. We do not use third-party advertising cookies.
You can disconnect a chess platform, opt out of public leaderboards, and export your data from Settings at any time.
You can delete your account. Deleting your account permanently removes your synced progress and stats from our database. To make a data access or deletion request, contact us at the address below.
Mainline is not directed to children under 13, and we do not knowingly collect information from them.
We may update this policy from time to time. The date above reflects the most recent version.
Questions about privacy? Email us at support@playmainline.com.