Privacy Policy

Last updated: 3/13/2026

Our Commitment

Susume Nihongo is completely free to use. We do not display advertisements, use analytics trackers, or include any third-party tracking scripts. Your learning experience is the only priority — we do not monetize your data in any way.

Local Storage

By default, all your data is stored locally in your browser using localStorage. No account is required to use the app. The following data is saved on your device:

  • Learning History: Your past queries and translations
  • Flashcards: Your personal flashcards with FSRS spaced-repetition data
  • Settings: Your preferences including language settings and theme choices
  • Quiz Progress: Kanji, kana, grammar, and vocabulary quiz statistics
  • Book Progress: Chapter completion status and reading progress
  • Book AI Conversations: Your Ask AI chat history for each book chapter
  • TTS Cache: Cached audio pronunciations to reduce API calls

API keys: Your Gemini API key is stored only in your browser's localStorage and is never transmitted to our servers. It is sent directly to Google's API endpoints when you make requests.

Authentication & Cloud Sync (Optional)

You may optionally sign in with your Google account to enable cloud synchronization. Authentication is handled by Supabase using Google OAuth. When you sign in:

  • What we store: Your Google display name, email address, and profile picture (provided by Google OAuth) are stored in our Supabase database solely to identify your account
  • Cloud Sync data: If you have an active Cloud Sync Pro subscription, your settings (excluding API key), learning history, flashcards, quiz progress, and book progress are synced to Supabase so you can access them across devices
  • What we never store: Your API key is always stripped before syncing. We never store passwords — authentication is fully delegated to Google OAuth
  • Data isolation: Your data is protected by Supabase Row Level Security (RLS) — only you can read or modify your own records
  • Subscription management: If you subscribe to Cloud Sync Pro, payment is processed via Stripe. We store only your Stripe customer ID and subscription status — no credit card details are stored on our servers

Signing in is entirely optional. All features of Susume Nihongo work fully without an account. Cloud sync simply allows you to keep your progress across multiple browsers or devices.

Third-Party Services

We use the following third-party services:

  • Google Gemini AI: To provide AI-powered Japanese translations, lessons, text-to-speech pronunciation, and chapter-specific Ask AI responses. Requests are sent directly from your browser to Google's API using your own API key
  • Google OAuth: For optional authentication when signing in with your Google account
  • Supabase: For user authentication and cloud data synchronization (only when signed in)
  • Stripe: For processing Cloud Sync Pro subscription payments (only if you subscribe)

No Ads & No Tracking

Susume Nihongo does not include any advertising networks, analytics trackers (such as Google Analytics), social media pixels, or fingerprinting scripts. We do not collect usage statistics, behavioral data, or any form of telemetry. The site does not set any third-party cookies.

Data Deletion

You can delete all local data at any time by clearing your browser's localStorage. If you have a subscribed account, you can delete your account and all associated cloud data through the account settings page.