Privacy Policy & Data Security

Susume Nihongo is structured to prioritize learning above all. We are entirely free to use. There are no trackers, no analytics SDKs, and no advertisements embedded in this application.

Because we operate on a local-first architectural model, your database remains localized on your computer. We do not monetize, evaluate, or aggregate your learning histories, cards, or speech conversations.

Your Google Gemini API Key is stored only inside the browser local sandbox. It is never routed through, processed, or logged on our servers.

Signing in with a Google account is optional. Translation, text-to-speech, guides, and quizzes work without an account. Signing in enables Cloud Sync and enhanced word highlighting in the listening-practice player.

• Supabase Authentication: Authentication is handled by Supabase OAuth with Google. We store your account ID, display name, and email. We do not store passwords.
• Listening-practice alignment: For signed-in users, generated audio and its expected Japanese text are sent through our authenticated Supabase function to Google Cloud Speech-to-Text. This transfer is used only to calculate word timestamps; the player still works with estimated timings if alignment is unavailable.
• Row Level Security (RLS): Our database utilizes strict RLS keys, ensuring that your synced flashcards are readable and writable solely by you.
• Stripe Checkout: Payments for Cloud Sync Pro are routed through Stripe. Stripe holds Level 1 PCI protection. We record your subscription status, but never see or store billing numbers.

Susume Nihongo runs as a Progressive Web App (PWA) on your devices. We register a client service worker (sw.js) to load page shells and CSS files offline.

This script does not collect, record, or share telemetry. Its sole role is optimizing resource speeds and providing complete offline compatibility for local pages.

The SusumeNihongo Chrome extension shows an action bar next to text you select on any page. It has no account and no API key of its own, and we operate no server that it talks to.

• The text you select. Sent out only when you press a button: Translate and Listen use Google’s public translation and speech endpoints, and AI uses Google Gemini. Nothing is sent while you are only reading.
• Your Gemini API key. Read from this site’s own browser storage and cached in the extension’s storage on your machine. It goes to Google and nowhere else — never to us.
• Cards you save. A saved card keeps the title and address of the page it came from. It stays on your device, and reaches your own account only through the same Pro sync as cards made in the app.
• Your extension settings. Whether the bar appears by itself, your keyboard shortcut, which side it opens on, and the sites you told it to leave alone — held in Chrome’s synced extension storage.

It contains no analytics, no advertising and no trackers, it reads nothing from a page until you select text there, and you can switch it off for any site — or every site — from its own settings.

You hold complete control over your local records. You can download or completely wipe your data at any time: