YubigakiPrivacy Policy
Last updated 10 November 2026. This policy covers the Yubigaki app and the website yubigaki.com.
In short
- Yubigaki keeps everything on your iPhone. It has no accounts, no analytics, no ads and no tracking. It sends nothing to me or to anyone else.
- A diagnostics log stays on your phone. It leaves only if you tap Share Log and send it yourself.
Who is responsible
The controller of your personal data under the GDPR is the developer of Yubigaki: Patryk Skibniewski, Poland. Email: support@yubigaki.com.
What the app stores on your iPhone
The app keeps these files in its own storage on your iPhone. Other apps cannot read them.
| Data | What it holds |
|---|---|
| Study progress | The kanji and kana you are learning or have marked as known, review dates and grades, answer times, your study days, your settings, and any study list you import. |
| Diagnostics log | What happened while you studied: sessions started and ended, grades, answer times, changed settings, errors. Each entry has the time, the app version and a random ID that changes at every launch. The log also records your iPhone model, iOS version and time zone. Up to about 10 MB; the oldest entries are dropped. |
| Stroke log | The points of every stroke you draw, which character and stroke it was meant to be, and how well it matched. Up to about 10 MB. |
| iOS reports | When iOS provides them, about once a day: summaries of how the app performs, such as launch time, hangs, memory use and crashes. |
None of this includes your name, an account, your location or your contacts. The app never asks for them.
The app works without the internet and does not connect anywhere, so these files never leave your iPhone on their own. Links in the app, for example to the data sources, open in your browser when you tap them.
The app needs your progress to work. The logs exist so that errors can be found and stroke recognition improved, but only if you choose to share them. Deleting the app deletes all of these files from your iPhone.
Sharing the diagnostics log, only if you choose
In Settings › Diagnostics Log, the button Share Log makes one zip file with the diagnostics log, the stroke log, the iOS reports and your study progress. The iOS share sheet opens and you choose where the file goes, for example an email to support@yubigaki.com. The file leaves your phone only then, and only to the place you pick.
If you send it to me, I use it only to find and fix errors and to improve stroke recognition. The legal basis is your consent, which you give by sending the file (Art. 6(1)(a) GDPR). You can withdraw it at any time by email, and I will delete the file. Withdrawal does not affect what was done before it.
I keep the file while I work on the problem, and no longer than 12 months. I may keep the strokes alone (their points, the character and the match result) longer as test data for stroke recognition, separated from your email address and from everything else in the file.
Emails to me
If you write to support@yubigaki.com, I receive your email address, your name if you include it, and your message. I use them to reply and to help you. The legal basis is my legitimate interest in answering you (Art. 6(1)(f) GDPR). I keep the conversation for up to 2 years after it ends, so I can see the history if you write again, and then delete it.
My mailbox for yubigaki.com is in iCloud Mail. In the EU, iCloud is provided by Apple Distribution International Ltd. (Ireland), which processes the messages on my behalf only to deliver and store them. Apple may store data with Apple Inc. in the USA; Apple bases such transfers on the EU Standard Contractual Clauses (Apple's privacy policy).
To sort support email and draft replies, I use an AI assistant (Claude, provided by Anthropic). It reads a message only to help me answer it, and I read and send every reply myself. Anthropic may process the message in the USA (Anthropic's privacy policy).
Purchases
Yubigaki 1.0 is free and has no in-app purchases. If tips or purchases are added later, Apple will handle them, and this policy will be updated before that version is released.
What Apple tells me
App Store Connect shows me statistics that Apple collects: downloads and, if you agreed in iOS to share analytics with app developers, crash reports and usage statistics. Apple collects these, not Yubigaki, and they do not identify you to me. You can turn this off in iOS: Settings › Privacy & Security › Analytics & Improvements › Share With App Developers.
Backups
iOS may include Yubigaki's files, such as your progress and the logs, in your iCloud Backup or computer backup, under Apple's terms. Yubigaki does not use iCloud itself and cannot read your backups. Copies in a backup stay there until that backup is replaced or deleted.
Sync between devices
Yubigaki does not sync between devices. If sync is added, this policy will be updated before that version is released, and it will say what data goes where.
This website
yubigaki.com is served from my own server in Poland. It sets no cookies, uses no analytics and loads nothing from other websites. The web server keeps no access logs. My router may record connection data (IP address and time) to protect the server; these records are kept only briefly and used for nothing but security. The legal basis is my legitimate interest in keeping the server secure (Art. 6(1)(f) GDPR).
No tracking, no ads
Yubigaki does not track you: it does not link data with data from other companies and shares nothing with data brokers or advertisers. It contains no ads and no third-party code that collects data. It makes no automated decisions about you. The app is meant for all ages and collects no data from anyone, children included.
Your rights
Under the GDPR you have the right to access your data, to correct it, to have it deleted, to restrict its processing, to receive it in a portable form, to object to processing based on legitimate interest, and to withdraw consent at any time. Write to support@yubigaki.com; I answer within one month. Giving me any data is voluntary.
Data that exists only on your iPhone is under your control: I cannot see it, so I cannot hand it over or delete it. You can look at it by sharing the log to yourself, and delete it by deleting the app.
You can complain to the Polish supervisory authority: Prezes Urzędu Ochrony Danych Osobowych, ul. Stawki 2, 00-193 Warszawa, uodo.gov.pl, or to the authority where you live or work.
Changes
When this policy changes, the date at the top changes too. If a new version of the app would handle data differently, for example send data off your phone, this policy is updated before that version is released.