PRIVACY POLICY - VOCABULARY CLOCK

Effective Date: July 15, 2026

Welcome to Vocabulary Clock. We respect your privacy and are committed to protecting your personal data. This Privacy Policy explains how we collect, use, store, share, and protect your information when you use the Vocabulary Clock mobile application and our backend services.

1. INFORMATION WE COLLECT

We collect information to provide a better, personalized learning experience and to sync your progress across devices. The data collected includes:

A. Account and Authentication Information

• Sign-Up/Login Data: If you register using email and password, we collect your email address and display name. If you sign in via Google Sign-In, we access your public profile information (email address, display name, and public profile picture URL).

B. User-Generated Content (UGC)

• Custom Vocabulary Sets: Any vocabulary words, definitions, topics, and custom flashcards you create.

• Uploaded Images: If you are a Premium user and upload custom images to illustrate your vocabulary cards, those files are uploaded and stored securely on our Cloudflare R2 cloud storage.

C. Learning Progress and App Configurations

• SRS Data: Spaced Repetition System (SRS) intervals, review history, learning status, session logs (e.g., response times, game scores, and learning types).

• Alarm Configurations: Your set alarm times, alarm rings, and notification schedules.

D. In-App Purchase and Transaction Data

• When you upgrade to Premium using Google Play Billing, we collect the receipt token (purchaseToken) and product identifier (productId) to verify and maintain your Premium status. We do not collect or store credit card numbers or any direct financial payment details.

2. HOW WE USE YOUR INFORMATION

We use the collected information for the following purposes:

• To synchronize your vocabulary sets, progress, and alarm configs across your devices.

• To verify, activate, and manage your Premium (VIP) subscription status.

• To send verification OTPs (One-Time Passwords) via email for account security and password recovery.

• To customize your learning flow and game selections.

• To monitor app performance and diagnose technical bugs (e.g., stale alarms, upload failures).

3. DATA STORAGE AND SECURITY

• Database Storage: Your profile details, progress statistics, and credentials are encrypted and stored on MongoDB Atlas secure cloud clusters. User passwords are one-way hashed using industry-standard hashing algorithms before saving.

• Media Storage: All user-uploaded vocabulary images are stored on secure Cloudflare R2 servers.

• Transmission Security: All communications between the mobile app and our servers are encrypted using HTTPS (SSL/TLS) protocols.

4. THIRD-PARTY SERVICES

To facilitate app operations, we integrate the following third-party services:

• Google Sign-In: For quick and secure authentication.

• Google Play Billing (In-App Purchases): For processing premium memberships securely.

• Mobile Advertising Networks (if active for free tier): For serving short video ads used to unlock system sets.

These third-party platforms govern their collected data under their respective privacy policies.

5. DATA RETENTION AND ACCOUNT DELETION (YOUR RIGHTS)

We believe in user control over personal data. You have the right to access, edit, and delete your vocabulary sets and account information.

• Account Deletion: You can request account deletion directly from the settings menu inside the application or by sending an email request to our support email listed below.

• Permanent Erasure: Once your account is deleted:

  • Your personal profile information and authentication credentials will be wiped from our database.

  • Your learning history, SRS records, and customized settings will be deleted.

  • All custom images you uploaded to Cloudflare R2 will be permanently deleted from our storage servers and cannot be recovered.

6. CHANGES TO THIS PRIVACY POLICY

We may update this Privacy Policy from time to time. Any changes will be posted on this page with an updated "Effective Date". We encourage you to review this policy periodically.

7. CONTACT US

For any inquiries, feedback, or requests regarding your data privacy and account deletion, please contact us at:

• Support Email: [nguyenhaoquang2004@gmail.com]

• To delete your account and all associated data, please email us at nguyenhaoquang2004@gmail.com. We will process your request within 24 hours