Kezi · Privacy

Privacy Policy

Effective 3 September 2026. English is the authoritative version.

Kezi collects as little as it can get away with. Nothing is sold, nothing is shared for advertising, and there is no advertising, analytics or tracking SDK in the app or on this website. You can use the entire app without ever giving us your name or email.

Who we are

Kezi is made and operated by an independent developer based in Vietnam, who is the data controller for everything described below. For any question about this policy, or to exercise any of the rights in it, write to hello@kezi.app.

What we store

Kezi is offline-first. Your learning data — which characters you have studied and your review history — is stored locally on your device. If Cloud backup is off, that is the whole story: nothing leaves your device at all.

With Cloud backup on, exactly these things reach our server:

• An account identifier. A random id generated on your device. On its own it is not linked to you.
• Your learning progress. Which characters you study, their review schedule, and your answer history — which exercise, right or wrong, and which character you confused it with.
• Learning settings. Daily goal, simplified or traditional, the language that explains Chinese to you, Hán-Việt on or off.
• Your email address — only if you sign in with Google. Nothing else from your Google account: no name, no profile photo, no contacts.

We never collect your contacts, location, photos, microphone, advertising identifier, or a device fingerprint. There is no crash reporter.

Cloud backup (optional)

Cloud backup is off until you turn it on. It exists so your progress survives a lost phone and follows you to a new one. Signing in is optional: without it, your progress is linked only to the anonymous identifier above — no name, email, or phone number. If you do sign in with Google, we also store the email address of that account, so your progress can be found again on another device. That is the only reason we store it, and we never send mail to it.

Why we may process this: to provide the backup and restore you asked for (performance of a contract), and — for the release-note list below — your consent.

No ads, no tracking

Kezi contains no advertising and no third-party analytics or tracking SDKs. We do not sell or share your data, and we do not use it to build a profile of you or to target anything at you.

Audio & notifications

Pronunciation uses your device's built-in text-to-speech voice; no audio is recorded or uploaded, and the microphone is never used. Reminders are scheduled locally on your device — we do not send push notifications and have no way to.

This website

The site sets no cookies and runs no analytics. Two things leave your browser, and only these two:

• The reading check. Text you paste is matched against the character list inside your own browser. It is never sent anywhere, and it is gone when you close the tab.
• The release-note list. If you submit the form, we store your email address and which language version of the page you used, so we can write once when the app ships. Nothing else, no other mail ever, and you can ask us to delete it at any time.

Who else can see it

We use as few outside services as we can, and none of them are analytics or advertising companies:

• Cloudflare hosts the app's backend, its database and this website. Like any host, it keeps short-lived technical logs (IP address, request time) for security and abuse prevention. We do not read them or connect them to any account.
• Google — only if you choose Google sign-in. Google tells us the account's identifier and email address so we can find your progress again. Google's own handling of your Google account is governed by its privacy policy, not ours.

That is the complete list. No other company receives your data, in any form, for any purpose.

Where your data is

Our backend runs on Cloudflare's global network, so data may be stored and processed outside your country, including outside Vietnam and outside the EU/EEA. It is encrypted in transit (HTTPS). Turning on Cloud backup is you asking us to do this; if you would rather nothing left your device, leave backup off — the app is fully usable that way.

How long we keep it

• Learning data and settings: until you delete them. We do not expire accounts or prune history.
• Sign-in tokens: a session token lasts 15 minutes; the token that renews it expires 60 days after its last use and is stored only as a hash. Signing out revokes it immediately.
• Release-note email: until launch, or until you ask us to remove it — whichever comes first.
• Deleted data: removed from the live database immediately. Cloudflare's routine backups may retain a copy for a short period before rolling over.

Children

Kezi is a study tool suitable for all ages, but it is not directed at children under 13 and we do not knowingly collect personal information from them. A child can use the entire app without an account: leave Cloud backup off and nothing is collected at all. If you believe a child has signed in and given us an email address, write to us and we will delete it.

Your rights

Wherever you live, you can ask us to show you what we hold about you, correct it, delete it, or give you a copy to take elsewhere. Most of that is already a button: Settings → "Delete all my data" removes everything, from your device and from our servers, without going through us at all. For anything else, write to hello@kezi.app and we will answer within 30 days.

If you are in Vietnam you have the corresponding rights under Decree 13/2023/NĐ-CP on personal data protection. If you are in the EU/EEA or the UK you also have the right to object to processing, to restrict it, to withdraw consent at any time, and to complain to your local data protection authority.

Deleting your data

Settings → "Delete all my data" clears your device and, if Cloud backup is on, your data on our servers. It is a real deletion, not a flag, and it cannot be undone — we cannot recover it for you afterwards. To be removed from the release-note list, write to the address above.

If this policy changes

We will update this page and change the effective date at the top. If a change materially affects what we collect or why, we will say so in the app before it takes effect, rather than quietly editing this page.

Contact

hello@kezi.app — for privacy questions, data requests, or anything else in this policy.