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.

Signing in

When you sign in with Google, Apple or GitHub, we receive your email and, where the provider offers it, your name and profile photo. Nothing else from that account is read. When you sign in with an email magic link, we send a one-time link via Resend. The same account works on the web and in the mobile app.

What you bring into the dojo

Texts you import into the Reader (pasted text or a book file), transcripts you add to the media library, and the cards you write are stored under your account and are private to you. We never publish or share them, and we never train anything on them. Deleting the item, or your account, deletes them.

Generated content and AI providers

Card audio and card illustrations are generated and stored by our service providers. Only the word being spoken or illustrated is sent — never your name, email or account id — and each result is reused by every learner of that word, so it never identifies you.

Some features send text to an AI or translation provider: tap-to-translate in the Reader, in Takeshi’s Tale and in the media library sends the word or sentence you tap; adding a card sends the word and its translation so an example sentence can be suggested; the conversational practice exercises send the text you type in that exercise so it can be answered or corrected. In every case the input is sent on its own, without your name, email or account id, and the result is cached and reused across learners, so it is not tied back to you. If you never open these features, nothing is sent.

Notifications

The mobile app can send push notifications (a study reminder, a streak at risk) and we may send occasional product emails. Both are delivered through OneSignal. To do that we share an anonymous device token, your email, your app language and a handful of study facts (whether cards are due, your streak, whether you have Pro) so a reminder can be relevant. You can turn push off in your device settings or in the app under Self → Notifications; every email carries an unsubscribe link, and unsubscribing is honoured immediately and stays in force unless you opt back in yourself.

Payments

If you subscribe to Pro on the web, payments are processed by Stripe. In the mobile app, purchases go through the Apple App Store or Google Play under their own terms. In all cases your subscription status is brokered by RevenueCat. Your card details are handled by the payment provider and are never stored on our servers — we keep only your subscription state and an internal billing id.

The feedback board

Everything you post on the feedback board (feedback.kotobadojo.com) is public, shown with your samurai name. Please don’t put anything there you wouldn’t want seen. Reports of a problem sent from inside the app go only to us.

How you found us

When an account is created we record, once, the campaign link it came from (the UTM parameters and landing page, if any). This lets us see which channels bring learners who stay. It is stored on our server with your account and nowhere on your device, and it is removed with the account.

Crash reports and analytics — with your consent

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.

Who processes your data

We rely on a small number of service providers, each receiving only the minimum needed for its function and none allowed to use it for its own purposes: Google Cloud (hosting, database, file storage, text-to-speech, translation), Cloudflare (card illustrations and their storage), Anthropic (AI text), Resend (sign-in and account email), Stripe, Apple, Google Play and RevenueCat (payments and subscriptions), OneSignal (push and email notifications), Upstash (rate limiting), and — only with your consent — Sentry and PostHog.

Some of these providers operate outside the European Economic Area, mainly in the United States. Where your data leaves the EEA, it is transferred under the European Commission’s Standard Contractual Clauses or another approved safeguard.

Your rights, deletion and retention

You can delete your account at any time from Self on the web or in the mobile app. Deletion is immediate and cascades to every record we keep about you, including your notification subscription. 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.

We keep your data for as long as your account is active. If you stop using Kotoba Dōjō entirely — no training sessions for 24 months — we anonymize the account rather than letting it sit indefinitely: your email, name, avatar name and any billing identifiers are permanently removed and your sign-in is severed, while anonymous study statistics and any decks you contributed are kept and can no longer be traced back to you. You never have to wait for this — you can delete your account outright at any time from Self.

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: 27 August 2026 · Questions: privacy@kotobadojo.com