Privacy information

Data kept in your browser

Lesson documents, teacher notes, author answers, standalone tool drafts, interface preferences and export presets may be stored in browser storage on your device. Local storage remains the primary editing workspace even when cloud backup is enabled.

Optional Google sign-in

When sign-in is configured, authentication is handled by Supabase Auth and Google OAuth. The application requests the OpenID, basic profile and email scopes needed for sign-in. Authentication providers may process account identifiers, profile information, email address, authorization data and session information under their own policies.

Signing in does not by itself upload lesson documents, teacher notes or tool drafts. Cloud transfer happens only after you explicitly save or restore a cloud backup.

Manual cloud backup

When Supabase cloud storage is configured, a signed-in user can explicitly save a complete lesson or standalone tool draft to the cloud. A cloud copy can include teacher notes, author answers, hidden tiles and other content inside that document. Cloud rows are associated with the authenticated user ID and protected by database row-level security.

Restoring or deleting a cloud copy also requires an explicit action in the account panel. Deleting a cloud copy does not delete the browser copy, and clearing browser storage does not automatically delete an existing cloud copy.

Exports, links and sharing

Files and links you create can contain material you entered. Teacher JSON or teacher-facing exports may include answers, hidden tiles or private notes. Some position links may include the full position. Review the destination and contents before sharing.

Third-party services and links

Google and Supabase have their own privacy practices. Reference courses can also link to third-party rule sources. Opening an external site is subject to that site’s policies.

Your controls

• Export important lessons or tool drafts before changing browsers, devices or site data.
• Use Sign out to end the Mahjong Study authentication session on the site.
• Clearing this site’s browser storage can remove local material that you have not backed up. Existing cloud copies remain until you explicitly delete them or the account is removed.

Privacy questions

For privacy questions about Mahjong Study, contact support@mahjongstudy.com.

Changes to this page

If the product later adds payments, analytics, automatic synchronization, collaboration or online assignment collection, this privacy information should be updated before those data paths are treated as part of the service.