Privacy Policy

Sakubo – Japanese Dictionary & SRS Tool

Last updated: March 6, 2026

SUMMARY
Sakubo collects your email address for account creation and syncs your study data to enable cross-device access and to improve the app. We will NEVER sell your personal data. Anonymized study statistics may be used for academic research on app improvement, language learning, and spaced repetition.

  1. INFORMATION WE COLLECT

When you create an account and sync your data, we collect the following:

Account Information:

  • Email address and password (password is hashed and never stored in plain text)

Study Progress (SRS Data):

  • Spaced repetition card states (ease factor, repetition count, interval, due date, accuracy, streak)
  • Per-skill breakdowns (vocabulary, kanji, grammar, handwriting, reading, meaning)
  • Review timestamps and session history

Daily Activity Statistics:

  • Items reviewed per day
  • New items learned per day
  • Words read per day

Drill & Practice Statistics:

  • Drill session results (type, correct/total answers, accuracy, duration)
  • Time attack scores and session data

Reading Statistics:

  • Words read per day
  • Reading time per session
  • Number of texts read

Custom Lesson Data:

  • User-created lesson names, descriptions, and word lists

All study data listed above is synced to our servers when you sign in and sync your account. Without an account, all data stays entirely on your device.

  1. INFORMATION WE DO NOT COLLECT
  • Device identifiers, advertising IDs, or hardware information
  • Location data
  • Contacts, photos, or other personal files
  • Browsing history or app usage analytics
  • Crash reports sent to third parties
  1. HOW WE USE YOUR DATA

Account & Sync: Your email authenticates your account. Your study data is synced so you can access it across devices.

Research & Improvement: We use anonymized, aggregated study statistics to understand how people learn Japanese and to improve Sakubo. This includes analyzing patterns such as review frequency, retention rates, learning curves, the effectiveness of different study methods (e.g., kanji study vs. vocabulary-only approaches), and drill performance. This data may be used for academic research, publications, or thesis work on language learning and spaced repetition. All research data is stripped of personally identifiable information and cannot be traced back to individual users.

App Development: Aggregated usage patterns help us identify which features are most effective and where the app can be improved.

  1. DATA SHARING

We DO NOT SELL your personal data. EVER.

We may share data only in these limited circumstances:

Service Providers: We use Supabase (https://supabase.com/privacy) for authentication and data storage. Your data is protected by row-level security policies ensuring users can only access their own data.

Academic Research: Anonymized, aggregated statistics only — NEVER individual user data.

Legal Requirements: If required by law, regulation, or valid legal process.

  1. DATA STORAGE & SECURITY
  • Cloud data is stored on Supabase infrastructure with row-level security.
  • Passwords are hashed server-side and never stored in plain text.
  • Authentication tokens are stored in your device’s private app storage.
  • All network communication uses HTTPS encryption.
  • Study data synced to our servers is associated with your user ID, not your email, for data separation.
  1. YOUR RIGHTS

Access: Your study data is visible within the app at any time via the My Stats screen.

Deletion: You may request deletion of your account and all associated cloud data by contacting us at the email below. Upon deletion, all synced data (SRS progress, custom lessons, activity statistics) will be permanently removed from our servers.

Offline Use: You can use Sakubo entirely without an account. No data leaves your device unless you create an account and sync.

Opt Out of Sync: You can use the app without signing in. All features work offline after the initial dictionary/local LLM download.

  1. CHILDREN’S PRIVACY

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

  1. THIRD-PARTY SERVICES

Supabase: Authentication and cloud data sync. Privacy policy: https://supabase.com/privacy

GitHub Releases: Dictionary database download on first launch. No user data is sent.

Liquid AI LEAP SDK: Small local, on-device LLM translation model. Runs entirely on your device with no data sent externally.

  1. CHANGES TO THIS POLICY

We may update this policy from time to time. Changes will be posted on this page with an updated effective date. Continued use of the app after changes constitutes acceptance of the updated policy.

  1. CONTACT

Questions or requests regarding your data?

Email: support@sakubo.co
Website: sakubo.co