Cookies and local storage
Last updated 25 September 2026
MainLine doesn't use advertising, analytics or tracking cookies, and it doesn't let third parties set cookies. Everything below is strictly necessary for a feature you choose to use, which is why the app doesn't show a consent banner.
Cookies
| Name | Purpose | Lifetime |
|---|---|---|
ml_session | Keeps you signed in after you choose Sign in with Lichess or Sign in with Chess.com. HttpOnly, first-party, only set if you sign in. Removed when you sign out or delete your account. | 1 year |
ml_oauth | Protects the Lichess and Chess.com sign-in step against forgery (a one-time code). Only set while signing in. | 10 minutes |
On-device storage
Your repertoires, training history, cached opening statistics and settings (theme, board, font) are kept in your browser's or app's local storage and IndexedDB, so MainLine works offline and without an account. They never leave your device unless you sign in to sync. The web app also stores its own files for offline use (a service worker cache).
Removing them
Settings → Your data → Erase all data on this device clears all of it. You can also clear site data in your browser settings. Blocking cookies only stops sign-in from working; everything else keeps working.
More
See the privacy policy and the terms of use. Questions: https://github.com/Tony11-dot/mainline/issues.