Privacy Policy

CJK Characters | Effective Date: May 19, 2026 | Version 1.0 (added Ad SDK + Crashlytics)

RedMoon Studio ("Company", "we", "us") operates the CJK Characters mobile application. This Privacy Policy explains how we handle information when you use our app.

1. Information We Collect

What We Do NOT Collect

CJK Characters does NOT collect any of the following:

• Personal identifiers such as name, email, phone number, date of birth
• Location data (GPS)
• Contacts, call history, or SMS
• Advertising identifiers (Android Advertising ID)
• App usage statistics, device information, network information
• Crash data or analytics data

Data Stored Only On Your Device

The following data is stored exclusively on your device and is never transmitted to any external server:

2. App Permissions

CJK Characters requests the following permissions only for the stated purposes:

CJK Characters does not request any sensitive permissions such as camera, photos/media, location, contacts, or microphone.

3. When the App Communicates Externally

CJK Characters v1.0 accesses the Internet only in the following two cases. Otherwise, it operates entirely offline.

1. Google ML Kit handwriting model download: On the first use of the "Handwriting" search feature, the app downloads the Chinese-script handwriting model (zh-Hani, approx. 20MB) once via Google Play Services. The model is stored locally, and all subsequent recognition happens entirely offline. Your handwriting strokes are NEVER transmitted externally.
2. Opening external links: When you tap "Feedback" or "Privacy Policy" in Settings, the OS default mail app or browser opens. We are not involved in this communication.

4. How We Use Information

We do not transmit any personal information externally. Your data is processed only on your device for the following purposes:

1. Learning Features: Flashcard study, 4-option multiple choice quiz, glyph matching, spaced repetition algorithms (SM-2 / FSRS-4.5)
2. Character Dictionary Search: SQLite + FTS5 based unified Korean/Chinese/Japanese character lookup
3. 4-script Comparison: Side-by-side display of Korean / Traditional / Simplified / Shinjitai slots
4. Statistics Display: Visualizing your own learning progress on a 30-day line chart
5. Pronunciation (TTS): OS system TTS or bundled offline mp3 audio for KR/CN/JP pronunciation playback

5. Third-Party Sharing

We do not share any personal information with third parties.

Third-Party Services (SDKs)

CJK Characters uses the following Google libraries:

• Google ML Kit (Digital Ink Recognition): Handwritten character recognition. Your stroke data is processed entirely on-device and is never transmitted to Google. The app does communicate with Google Play Services once when downloading the recognition model. Google's ML Kit privacy policy: developers.google.com/ml-kit/terms
• Google AdMob (Advertising): Displays banner ads on dictionary screens and interstitial ads during study sessions. Your Android Advertising ID, approximate geographic location, and device information may be sent to AdMob for ad personalization. You can reset your advertising ID or opt out of personalized ads via Android Settings → Google → Ads. Google's advertising privacy policy: support.google.com/admob/answer/6128543
• Firebase Crashlytics (Crash Reporting): When the app crashes, non-identifying diagnostic data — crash stack traces, device model / OS version / app version — is sent to Google to help us improve stability. No personally identifying information (name, email, study data) is included. Firebase privacy policy: firebase.google.com/support/privacy

CJK Characters does NOT use analytics SDKs (e.g., Firebase Analytics) or rewarded / tracking SDKs.

If this SDK list changes in the future, this Privacy Policy will be updated and announced in app release notes in advance.

6. Data You Voluntarily Share

The following data is processed only when you take explicit action:

• Character sharing: When you tap "Share" from a search result or the comparison screen, the character and meaning are passed to the OS share sheet (KakaoTalk, Messages, mail, etc.). We are not involved in this transmission.
• Learning result sharing: After a quiz session, you may share your accuracy / statistics yourself.
• Feedback / Error report email: When you write an email via Settings > Feedback or the "Report Error" menu on the character detail screen, only the content you type is sent to our email (teamstar13000@gmail.com).
• Share intent (incoming): When another app shares text containing characters into this app, the app receives the text and auto-fills the search box. The received text is processed only on-device and is never transmitted externally.

7. Data Retention and Deletion

We do not store any user data ourselves. All data is stored on your device and can be deleted as follows:

• App uninstallation: All learning data, favorites, user decks, and settings are immediately and permanently deleted.
• In-app data clearing: User decks / favorites / recently viewed can be individually deleted from the respective screens.

8. Your Rights

1. Data access: View all your learning data on the Study tab statistics screen
2. Data modification/deletion: Delete decks / favorites / recents directly from the in-app screens
3. Complete data deletion: Uninstall the app to immediately delete all data

9. Children's Privacy

CJK Characters does not knowingly collect personal information from children under the age of 13. Since this app does not transmit any personal information externally, there is no possibility of children's personal information being leaked. This app is provided for the educational purpose of character study and is rated "Everyone" (IARC).

10. Security

• All user data is stored only on the device (no external server)
• User input (deck names, etc.) uses SQLite parameterized queries to prevent SQL injection
• No account / authentication system, so no credential leak risk
• All external communication (ML Kit, mailto, external URLs) uses HTTPS or OS-standard IPC

11. Data Sources and Attribution

The character dictionary data bundled in the app is integrated from the following public / licensed data sources; it is not user-input. For detailed licenses, please refer to the "Open-source Licenses" screen inside the app.

• Unicode Unihan Database / CC-CEDICT / KanjiDic2 / JMdict
• Korean Standard Dictionary / Korea Hanja Society
• HSK 1~6 / Taiwan MoE / Japan Jouyou Kanji / Jinmei-yo
• Make Me a Hanzi (stroke order data)
• Wiktionary (ko/ja/zh)
• Noto Sans fonts (Adobe SIL OFL)

12. Changes to This Policy

If this Privacy Policy changes, the changes will be notified through app updates or on this page. Material changes (e.g., adding third-party SDKs, expanding data collection scope) will be announced 7 days before they take effect.

13. Contact Us