Privacy Policy

Last updated: March 6, 2026

1. Overview

CheesCoach is a chess coaching application for Android developed by JuanfranDevs. This privacy policy explains how our application handles your data. We are committed to protecting your privacy and being transparent about our data practices.

Key principle: CheesCoach is designed to be privacy-first. All your chess data is stored locally on your device. We do not collect, store, or transmit personal information to our servers — because we don't have any.

2. Data Collection

CheesCoach does not collect any personal data. The app works primarily offline and stores all information locally on your device.

Data stored locally on your device:

Data Type	Purpose	Storage
Chess games (PGN)	Saving and reviewing your games	Local database (Room)
Move analysis	Caching AI analysis to avoid repeated API calls	Local database (Room)
API keys	Authenticating with AI providers you choose	Encrypted (AES-256-GCM)
App preferences	Theme, ELO level, board colors	DataStore Preferences
Puzzle progress	Tracking your puzzle rating and streaks	DataStore Preferences

Data we do NOT collect:

• Personal information (name, email, phone number)
• Location data
• Device identifiers or advertising IDs
• Usage analytics or telemetry
• Crash reports (no crash reporting SDK is used)
• Contacts, photos, or any other personal files

3. AI Services & Third-Party APIs

CheesCoach can connect to third-party AI services to provide educational chess commentary. This feature is entirely optional and requires you to provide your own API key.

Supported AI providers:

• Google Gemini — Privacy Policy
• OpenAI — Privacy Policy
• Anthropic (Claude) — Privacy Policy
• DeepSeek — Privacy Policy

What data is sent to AI providers:

When you use the AI coaching feature, the following chess-specific data is sent to your chosen AI provider:

• The current chess position (FEN notation)
• The game move history (PGN notation)
• The Stockfish engine evaluation (numeric score)
• Your configured ELO level (for adjusting explanation complexity)

No personal information is ever sent to AI providers. Only chess positions and game data are transmitted. Your API key is sent as an authentication header but is never shared with us.

API key handling:

• Your API keys are stored exclusively on your device
• Keys are encrypted using AES-256-GCM via Android's EncryptedSharedPreferences
• Keys are only used to authenticate API requests — they are never logged, transmitted to us, or shared with any other party
• You can delete your API keys at any time from the app's Settings screen

4. Lichess Integration

CheesCoach offers optional online play through Lichess.org, a free and open-source chess platform.

Authentication:

• Lichess login uses OAuth 2.0 with PKCE (industry-standard secure authentication)
• CheesCoach never sees or stores your Lichess password
• The OAuth token is stored encrypted on your device and can be revoked at any time

Data exchanged with Lichess:

• Your Lichess username and rating (for display in the app)
• Game moves and clock data during online matches
• Game seek parameters (time control, color preference)

For details on how Lichess handles your data, see the Lichess Privacy Policy.

5. Data Storage & Security

• All data is stored locally on your Android device
• Chess games and analysis are stored in a local SQLite database (Room)
• Sensitive data (API keys, OAuth tokens) is encrypted using AES-256-GCM
• Preferences are stored in Android's DataStore
• The Stockfish chess engine runs entirely on your device — no server processing
• CheesCoach does not have any backend servers — we cannot access your data

6. Data Sharing

CheesCoach does not sell, rent, or share your personal data with any third party. The only data transmitted from the app is:

• Chess position data sent to AI providers only when you actively request analysis (optional feature)
• Game data exchanged with Lichess only during online play (optional feature)

The app contains no ads, no trackers, and no analytics SDKs.

7. Children's Privacy

CheesCoach does not knowingly collect any personal information from children under 13 years of age. Since the app does not collect personal data from any user, it is safe for children to use. However, if a child uses the optional AI coaching or online play features, data will be transmitted to third-party services as described above.

Parents or guardians should be aware that the AI coaching feature requires an API key and may incur costs from the AI provider. We recommend parental supervision for this feature.

8. Your Rights

Since all your data is stored locally on your device, you have full control:

• Delete your data: Clear app data from Android Settings, or uninstall the app
• Delete API keys: Remove them from the Settings screen within the app
• Revoke Lichess access: Disconnect from Settings or revoke the token from your Lichess account
• Export your games: Games can be exported as PGN files at any time
• Disable AI features: Simply don't add an API key — the app works fully offline

9. Changes to This Policy

We may update this privacy policy from time to time. Any changes will be posted on this page with an updated revision date. We encourage you to review this policy periodically. Continued use of the app after any changes constitutes acceptance of the updated policy.

10. Contact

If you have any questions or concerns about this privacy policy, please contact us:

• Developer: JuanfranDevs
• GitHub: github.com/juanfranj