PRIVACY
Privacy policy
Last updated: October 24, 2026
Long Ký ("the app") is a Vietnamese-history reading app built by an independent developer. This policy explains what Long Ký collects — and, more to the point, what it doesn't.
1. The app collects no personal data
Long Ký has no sign-up or sign-in. It does not collect your name, email, phone number, location, or any other personally identifying information. It does not track you across other apps or websites, and carries no advertising. Section 8 below describes the anonymous usage statistics the app does send.
2. Content is fetched from a server
The app's historical text and images are fetched from a content-delivery network (Cloudflare R2) to keep the app small and up to date. This fetch is not tied to your identity; the server may keep ordinary technical logs (such as IP address and request time), as any web server does, solely to operate the service — never to identify you.
3. In-app purchases
Long Ký offers "Mời Long Ký một chén trà" — a voluntary tip to the developer, not a charitable transaction — bought through Google Play Billing (three sizes: one, two or three cups). All payment information (card, account) is handled directly by Google Play under Google Play's own privacy policy. Long Ký never sees or stores your payment details — it only receives the transaction's outcome (succeeded/failed) to show a thank-you message.
4. On-device storage
The app stores a small amount of data on your own device only (never sent to any server we run): a downloaded content pack for offline use, and your quiz progress (best score per mode, and whether you've completed today's quiz), the pages you have opened, and your picture-unlock progress (which pictures are open, the daily gift, your streak and today's unlock count). This data lives only on your device; uninstalling the app removes it.
5. Not directed at children, but suitable for all ages
Long Ký is not specifically directed at children and collects no data from anyone, children included. Its content is suitable for anyone interested in Vietnamese history.
6. Changes to this policy
If this policy changes, the new version will be posted at this same address, with the updated date at the top.
7. Contact
Questions about privacy? Contact: help@long-ky.com
8. Anonymous usage statistics and crash reporting
Long Ký uses Firebase Analytics and Firebase Crashlytics (both Google services) and PostHog to see which pages get read, how long readers stay on each, and to catch crashes and errors. These record: which screens you view and how long each stays open, how far down an event page you scroll, in-app actions (e.g. playing Câu đố, opening Chào cờ, listening to a narration, dragging the territory atlas, opening the tip sheet, opening the daily gift or unlocking a picture, keeping or losing a streak), your reading language and content version, your device model and OS version, an estimated country, and a random device identifier that Firebase and PostHog generate — never your name, email, or any account of yours. The app never records your screen. When the app hits an error, information about that error (not the content you were viewing or entering) is also sent, to help fix it. Google processes the Firebase data under its own Privacy Policy; PostHog stores its data on its servers in the United States and processes it under its own Privacy Policy.
You can turn this off at any time under Sảnh → Về Long Ký → "Share anonymous usage stats". It is on by default.
9. Mistake-report emails
The "Báo sai sót" (Report a mistake) button on event and figure pages opens an email draft in your own mail app. It is sent only if you send it yourself, and contains only what the draft shows (the page, the app and content versions, the language, and your note) plus your email address. We use it only to fix the content and to reply to you; the app itself stores and sends nothing.
10. Daily reminders (notifications)
If you agree, Long Ký can remind you once a day with a page of history and a note that your daily gift is waiting. The app asks only after you have used it for a while, and gently asks again after every 5th gift you open if the reminder is still off. These are local notifications scheduled by your own phone: no server push, nothing is sent anywhere, and the app asks for the system's notification permission only after you choose to turn it on. You can turn it off at any time in the Sảnh or in your phone's Settings.