Privacy Policy
1. Overview
Kardio helps you create, study and master flashcards using smart repetition and AI-powered tools. This policy explains what information we collect, why, who we share it with, and how you can see or delete it. Kardio is designed to comply with the Apple App Store guidelines, the UK GDPR and Google Firebase's security standards.
2. Information we collect
a. Personal information
- Email address and password, if you sign up with an email address. Your password is handled by Firebase Authentication and is never visible to us. Your email is never shown to other users.
- Sign in with Apple or Sign in with Google, if you choose one of those instead. Apple or Google confirms who you are and passes us your email address, and your name the first time only. We never see your Apple or Google password. If you pick Apple's Hide My Email, Apple gives us a relay address ending in privaterelay.appleid.com rather than your real address, and that relay address is the one Kardio stores and uses.
- Profile information: username, display name, optional bio and avatar. These appear next to decks and reviews you share. You can switch your public profile off in Settings.
b. Study data
- Decks and cards you create or import. Decks are private unless you choose to make one public.
- Documents, text and links you submit for AI card generation (see section 8). Uploaded files are kept in your private storage folder so you can generate again.
- Study progress: which cards you have seen, how you graded them, when they are next due, streaks, daily counts and goals.
- Reviews, ratings and reports you post about public decks.
Study data is under your control: you can edit or delete it in the app at any time.
c. Device permissions (all optional)
- Camera — to scan documents or take a photo for a card.
- Photo library — to add an image to a card or set an avatar.
- Microphone — to record audio for a card.
- Notifications — for the daily study reminder, only if you turn it on.
You can change any of these later in your device's Settings.
d. Usage information
Kardio records a short, fixed list of things that happen in the app — currently 18 of them — so we can see which features are used and where people get stuck. For example: the app was opened, an account was created, a deck was made, a study session was started or finished, a card was graded, a deck was made public, a report was filed, an account was deleted.
Each one carries counts and settings only: how many cards were in the session, how many you got right, how many seconds it took, which sign-in method you used, which theme you picked. Stored alongside them are your Kardio account id, whether you are on iPhone, Android or the web, and which version of the app you are running. They never include your card text, deck names, email address or username, and our server rejects anything that is not on the list.
Kardio contains no crash-reporting tool and no third-party analytics service, so we do not track you screen by screen and we do not receive automatic crash reports from the app. We do not build advertising profiles and we do not collect your precise location or your contacts. Kardio has no in-app purchases and does not collect payment details.
When you delete your account, everything tied to it is deleted, including these usage records.
3. How we use your data
- To provide and improve the Kardio service.
- To sync your decks and progress across your devices.
- To track your progress, streaks and daily goals.
- To send optional study reminders or updates you have opted into.
We never sell your personal data and we do not share it with third parties for marketing.
4. Storage and security
Your account and study data are stored in Google Firebase (Authentication, Firestore and Storage). Data is encrypted in transit and at rest. Access is controlled by Firebase Authentication and security rules, so no other Kardio user can read your private decks, your study progress, or the documents you upload for AI card generation. Kardio is run by one person, who can reach this data when it is needed to run the service or to look into a report, and does not do so otherwise.
Pictures and voice recordings on cards work differently. Card images, card audio and deck cover pictures are stored as files in Firebase Storage, and each one is served through a long, hard-to-guess web link. That is what lets a public deck — and the copies other people make of it — still show its pictures. Anyone who has that exact link can open the file, even if they are not signed in to Kardio. So these files are not private to you: please do not put anything sensitive in a card image or a voice recording.
Our own small server, hosted on Vercel, sits between the app and the AI provider. It stores a daily generation counter, the usage records described in section 2d, and plain statistics about each AI request (which mode you chose, how many cards came back, how much AI capacity it used) — not the material you sent. If you rate a generated card with a thumbs up or thumbs down, it also stores that rating and any note you choose to type with it. Our hosting providers, Vercel and Google, keep ordinary request logs that include your IP address, as part of running the service.
Deleting your account removes your decks, study history, profile, uploaded files and usage records.
5. Data retention
We keep your data for as long as your account is active. When you delete your account, everything tied to it is deleted — your decks, cards, study history, profile, uploaded files and usage records — and it is erased within 30 days (the app removes it immediately; backups held by our hosting provider are overwritten on their normal schedule). Reports you filed about other content may be kept in anonymised form so we can spot repeat problems.
6. Children's privacy
Kardio is not intended for children under 13 and we do not knowingly collect information from them. If you believe a child under 13 has created an account, contact us and we will delete it.
7. Your rights
You can:
- View and edit your profile and study data in the app.
- Delete your account and data in Settings → Delete Account, or by email — see Delete your account.
- Request an export of your decks, cards and progress by emailing us.
To exercise any of these rights, or to ask a question, contact coopj1978@gmail.com. If you are in the UK you can also complain to the Information Commissioner's Office (ico.org.uk).
8. Third-party services
- Google Firebase — authentication, database and file storage. We do not use Firebase Analytics.
- Vercel — hosts our API server and this website. Like Google, Vercel logs the requests it handles, including IP addresses.
- Apple and Google sign-in — if you sign in with Apple or Google, they confirm your identity to Firebase Authentication. Apple's Hide My Email gives us a relay address instead of your real one.
- Anthropic (Claude) — AI card generation. When you ask Kardio to write cards, the text or document you submitted is sent from our own server to Anthropic, which returns the cards. Only the material for that request is sent — never your account details, other decks or study history. Anthropic processes it on our behalf and does not use it to train its models. Please only upload material you have the right to use.
- The Apple and Google app stores — download and install statistics. If you have turned on sharing with developers in your device settings, they may also show us anonymous crash statistics. Kardio itself contains no crash-reporting tool.
Other Kardio users can see the decks you make public, your reviews, and your public profile (and your study stats, if your profile is public).
9. Changes to this policy
We may update this policy from time to time. The latest version is always available in the app (Settings → Privacy Policy) and on this website. If a change is significant we will let you know in the app before it takes effect.
10. Contact
Kardio is operated from the United Kingdom. Email coopj1978@gmail.com with any questions about this policy or your data. This policy is governed by the law of Scotland, and the Scottish courts have jurisdiction over any dispute, without affecting the consumer rights you have where you live.