Privacy Policy
Official version, effective 18 October 2026
The short version
- Hornbook has no account and no sign-in.
- Your drill results, progress and settings stay on your phone. They are not sent to us or to anyone else, and the app asks your phone to leave them out of cloud backups.
- Hornbook contains no analytics, advertising or tracking code.
- The app goes online for three things only: downloading chart packs, getting the unlock key for a Pro pack, and buying or restoring a subscription through the App Store or Google Play.
- We do not keep any of the data those requests carry.
1. Who we are
Hornbook is published by Nguyen Phuong Ngoc, an individual developer, Apartment 1411, Block CT1 A10 Nam Trung Yen Condominium, Yen Hoa Ward, Hanoi, Vietnam 11213 ("we", "us"). Contact: [email protected].
2. What stays on your phone
These are created and stored only on your phone:
- your drill answers, scores, leak statistics and spaced-repetition schedule;
- your settings, such as the app language;
- the chart packs you download;
- a small record of your subscription status (Pro or not, the plan, when it was last checked and when it ends), so Pro works offline. It holds no payment details, no store account and no purchase number.
None of this is sent off your phone. Hornbook has no feature that uploads it, and we have no server that could receive it.
3. What leaves your phone, and why
| When | What is sent | Sent to | Why | Kept by us |
|---|---|---|---|---|
| You open the Packs screen (at most once a day) or download a pack | A request for the pack list or for pack files. Like any internet request it shows your IP address, and the file names show which pack and version you download. The app sends a fixed app label, no cookie, no device ID and no user ID. | Cloudflare, which hosts our pack files | To deliver the files | Nothing |
| You install or update a Pro pack | Your purchase reference (the App Store transaction number or the Google Play purchase token), the product, the pack and version, the platform (iOS or Android) and a public key created at random by the app on your phone, plus technical values that name the pack build and your phone's key format, and your IP address | Our key service, which runs on Cloudflare | To check with Apple or Google that your subscription is active, then return the pack key locked to your phone | Nothing |
| The key service checks your subscription | The App Store transaction number (to Apple), or the app's package name and the purchase token (to Google) | Apple or Google | To confirm the subscription | Nothing |
| You buy, restore or renew a subscription, or the app checks your subscription status | What the App Store or Google Play needs to process the purchase | Apple or Google, through your phone's store | Payment and subscription management | We receive no payment details |
Your IP address is used only to deliver each response. The key service also counts requests per IP address in memory for up to one minute to block abuse; the count is never written down.
Your phone's operating system may send crash reports and usage statistics to Apple or Google if you allowed this in your phone's settings. Apple and Google may show us summaries of these in their developer consoles. Hornbook does not add anything to these reports.
4. What we do not do
- No account, sign-in, email address or phone number.
- No analytics, advertising or tracking code, and no advertising ID.
- No access to your contacts, location, photos, camera or microphone.
- No reading of your screen or of other apps, and no connection to any poker site or poker software.
- Your hand histories and study data are never uploaded.
- We do not sell or share personal data.
If we ever add optional analytics, it will be off until you turn it on, and this policy will change first.
5. Companies involved
- Cloudflare, Inc. hosts the pack files and runs our key service. It processes IP addresses and request data on our behalf. We have turned off logging for the key service and for the storage that serves the pack files, and we do not use Cloudflare analytics on these web pages. Cloudflare's own handling of network data is described in its privacy policy: https://www.cloudflare.com/privacypolicy/
- Apple and Google process your purchases and subscriptions under their own privacy policies: https://www.apple.com/legal/privacy/ and https://policies.google.com/privacy
6. How long data is kept
| Data | Where | How long |
|---|---|---|
| Study data, settings, packs, subscription status record | Your phone | Until you delete it or uninstall the app |
| Requests for pack files | Cloudflare | We keep nothing. Cloudflare may keep operational network logs under its own policy. |
| Key requests | Our key service | Nothing is stored; logging is off. The abuse counter lives in memory for up to one minute. |
| Purchases | Apple or Google | Under their policies |
7. Backups and new phones
Hornbook does not use iCloud or Google backup for its data. On Android the app opts out of cloud backup and of phone-to-phone transfer. On iOS the app marks its study data, settings, subscription record and packs as excluded from backup. This means your study data does not move to a new phone, and it is lost if you uninstall the app. Your subscription is not lost: use Restore purchases on the new phone. An optional backup setting may come in a later version; it will be off unless you turn it on.
8. Deleting your data
Everything Hornbook stores is on your phone, so you control it:
- uninstall the app to delete all of its data; or
- on Android, open your phone's Settings, then Apps, Hornbook, Storage, and clear its storage.
We hold no personal data about you, so there is nothing for us to delete on a server. To cancel a subscription, use your App Store or Google Play subscription settings; uninstalling the app does not cancel it.
9. Children
Hornbook is a study tool for adult poker players. It is not directed to children, and you must be at least 18 years old to use it. We do not knowingly collect data from children; in fact we collect no personal data from anyone.
10. Your rights
Depending on where you live, you may have rights to access, correct, delete or object to the use of your personal data. Because we keep no personal data about you, a request to us will usually find nothing to return or delete. For purchase data, contact Apple or Google. You can contact us at [email protected], and you may complain to your local data protection authority.
11. International processing
Cloudflare serves requests from data centers around the world, usually the one closest to you, so a request may be processed outside your country. Apple and Google process purchases under their own transfer safeguards.
12. Security
All network requests use HTTPS. Pack files are checked against a signed list before use. Pro packs are encrypted and their keys are locked to a key that stays on your phone.
13. These web pages
This page and our Terms page are static pages hosted by Cloudflare Pages. They contain no analytics script and set no cookie.
14. Changes
If we change what data leaves your phone, we will update this policy before the app version with that change is released and describe the change in the release notes. The effective date above shows the latest version.
15. Contact
Nguyen Phuong Ngoc, Apartment 1411, Block CT1 A10 Nam Trung Yen Condominium, Yen Hoa Ward, Hanoi, Vietnam 11213, [email protected]