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Privacy Policy

Last updated: July 24, 2026

This Privacy Policy explains what information ZeroNihongo ("the app", "we", "us") collects, how it is used, and the choices you have. ZeroNihongo is a Japanese-learning app for Android. By using the app, you agree to the practices described here.

1. Information We Collect

Account information

To sync your progress across devices, ZeroNihongo requires you to sign in using Firebase Authentication. Depending on the sign-in method you choose, this may include your email address, display name, and profile photo, or an anonymous account identifier if you sign in as a guest.

Learning progress

We store the data needed to run your lessons and reviews: which vocabulary, kanji, and grammar points you've studied, your spaced-repetition review schedule, quiz results, your selected Adaptive Immersion level, and related in-app settings. This data is stored in Google Firestore under an identifier tied to your account, so it can be restored if you sign in on a new device.

AI feature data

The AI Tutor, AI-generated quizzes, and Grammar Playground assistant send the text you enter (your questions, practice sentences, and the relevant lesson content) to an AI gateway service in order to generate a response. This content is used only to produce your in-app response and is not linked back to your identity by us beyond what's needed to serve the request.

Device identifier (referral program only)

If you use the referral program, the app reads your device's Android ID and sends it to our server, which immediately converts it into a one-way scrambled value (a salted hash) and stores only that. We never store the identifier itself, and the stored value cannot be reversed back into it or matched against any other app or service.

Its only purpose is to enforce the rule that each device can claim one referral reward. Without it, one person could create any number of accounts on a single phone and award themselves unlimited free premium, which would make the program impossible to offer. It is not used for advertising, analytics, tracking you across apps, or building any profile of you, and it is not shared with anyone. If you never use the referral program, it is never collected.

Information we do not collect

ZeroNihongo does not currently show ads, does not use third-party analytics or advertising SDKs, and does not sell or share your data with data brokers.

2. How We Use Information

  • To create and maintain your account and sync your progress across devices.
  • To generate AI Tutor responses, quizzes, and grammar feedback.
  • To operate, maintain, and improve the app, including diagnosing technical issues.
  • To communicate with you about your account or in response to a support request.
  • To prevent abuse of the referral program, using the hashed device identifier described above.

3. Data Storage and Security

Account and progress data is stored using Google Firebase (Authentication and Firestore). Firebase applies industry-standard security practices, and access to your data in Firestore is restricted by security rules to your own signed-in account. No method of transmission or storage is 100% secure, but we take reasonable steps to protect your information.

4. Data Retention and Deletion

Your progress data is retained for as long as your account exists. You can clear your local progress at any time from within the app's settings. If you would like your account and associated data permanently deleted from our systems, contact us at the email below and we will process the request within a reasonable timeframe.

5. Children's Privacy

ZeroNihongo is not directed at children under 13, and we do not knowingly collect personal information from children under 13. If you believe a child has provided us with personal information, please contact us so we can remove it.

6. Third-Party Services

ZeroNihongo uses Google Firebase (Authentication and Firestore) for account management and data sync, and a third-party AI gateway to power the Tutor, Quiz, and Grammar Playground features. These providers process data on our behalf and are bound by their own security and privacy commitments.

7. Changes to This Policy

We may update this Privacy Policy from time to time. Changes will be posted on this page with an updated "Last updated" date. Continued use of the app after changes take effect constitutes acceptance of the revised policy.

8. Contact Us

Questions about this policy or your data? Email us at zeronihongo.support@gmail.com.