Privacy policy

Katsuyokei · version 1.0.2 · last updated: 4 September 2026

Katsuyokei is an app for practicing Japanese conjugation, and it runs entirely on your device. This policy describes what version 1.0.2 actually does, not what is planned.

In short: the app collects nothing about you. There is no account, no server, no analytics and no advertising. Apart from handling a purchase, it makes no network request at all.

Your account

There is none. The app does not ask for an email address, does not create a profile, and does not sign you in anywhere. Installing and using it requires no personal details.

Where your study data goes

Progress, answer history, your day streak and your settings are written to the device storage alone. They are not sent anywhere. Deleting the app removes them with it; Settings also has a button that erases all progress.

Data shared with the developer's other apps

Katsuyokei belongs to a family of Japanese-learning apps, alongside Kaname (grammar), Joshi (particles), Kazoekata (counters), Bunmyaku (reading) and Kuzushi (casual speech). If you have more than one of them installed, the home screen shows a Your Japanese section with one row per app.

Here is how that works: Katsuyokei writes a small card file on your device, in an area shared by the apps in this family. The card carries six things about your studying: how much of the material you have mastered, how many days your streak runs, how many sessions you have done, one sentence about your weakest spot (in Polish and in English), whether today's goal is already met, and when your next reviews fall due. Plus three technical ones: which app wrote the file, in what format, and when. Nothing else. There is no answer history and no list of the items you practiced, and your progress cannot be reconstructed from this file.

The file never leaves your device, and it is read only by the other apps in this family that you have installed on that same device. There is no server and no account here, and nothing syncs between devices.

Two things worth saying plainly. First, the shared area survives uninstalling a single app — the file goes only once you remove every app in the family from the device. Second, “Erase all progress” deletes this file too, along with everything else.

Tracking and advertising

The app carries no advertising, does not use the advertising identifier (IDFA), embeds no analytics kit, and does not track you across other apps or websites. It does not ask for tracking permission, because there is nothing to ask about.

Network connections

The version shipped to the App Store makes no network request other than handling the in-app purchase, which the operating system carries out. All the study material ships inside the app, so it works with no internet and in airplane mode.

Purchases

The one-time purchase is handled by the App Store. All the app learns from the system is whether the purchase is valid. It neither sees nor stores payment details, an address, or your Apple Account identifier.

Contact and bug reports

“Suggest a feature” and “Report a bug” open your mail client with the message prepared. Nothing is sent automatically — you see the message before it goes and can change it freely or drop it.

A bug report has a block attached with the app version, the build number, the iOS version and the device series model (iPhone16,1, for instance). That is a name shared by millions of units and identifies neither the device nor a person. The block is visible in the body of the message and you can delete it before sending.

Crash reports

The app collects no crash reports of its own. If you have Apple analytics sharing turned on in iOS settings, the system may pass an anonymous report to the developer — that happens outside the app and is governed by Apple's privacy settings.

Children

The app is not directed at children under 13 and collects no data from anyone, at any age.

Changes to this policy

If any statement above stops being true, this page will be changed before the release that invalidates it, not after.

Contact

Privacy questions: jakub.dwojak+katsuyokei@hotmail.com