Privacy

We store the minimum needed to run the app: your email (sign-in), the name you give your samurai, the cards and decks you use, your study history, and your streak. We do not sell or share this data.

When you sign in with Google, we receive your email and profile photo from Google. When you sign in with email magic link, we send a one-time link via Resend.

Audio playback uses Google Cloud Text-to-Speech; the resulting audio files are stored on Vercel Blob and served back to you. Card illustrations are sourced from The Noun Project search and mirrored to Vercel Blob. The optional Pro example-sentence suggestion uses Anthropic (Claude); only the word and its translation are sent, and the result is cached so it never identifies you.

If you subscribe to Pro, payments are processed by Stripe and your subscription status is brokered by RevenueCat. Your card details are handled by Stripe and are never stored on our servers — we keep only your subscription state and an internal billing id.

Our infrastructure subprocessors are: Neon (database), Vercel (hosting + Blob storage), Google Cloud (sign-in & speech), Resend (email), Stripe + RevenueCat (payments), Sentry (crash reports), PostHog (analytics), Cloudflare, The Noun Project (illustrations), and Anthropic (Pro example sentences). Each only receives the minimum data needed for its function.

With your consent, we use Sentry to capture crashes and a brief replay of the error (no passwords, no email, no auth headers — see the consent banner for what each category covers). We use PostHog for anonymous funnel analytics — keyed by an internal user id, not your email or name. You can change either choice at any time from Self → Cookie preferences.

You can delete your account at any time from Self. Deletion is immediate and cascades to every record we keep about you. You can also export your data as JSON from the same screen. You have the right to access, correct, export, and delete your data, and to object to processing.

The data controller is Artsiom Chtrykov, the operator of Kotoba Dōjō, based in Poland (European Union). To exercise any of these rights, or to ask a privacy question, email privacy@kotobadojo.com. If you believe we have mishandled your data, you also have the right to lodge a complaint with your local EU data-protection authority.

Last updated: 1 June 2026 · Questions: privacy@kotobadojo.com