The KotsuKotsu app and website (the “app” and the “website”) do not collect personal information. There are no accounts or logins, and study history is stored only on your device and in your browser.
1. Personal information we collect
The app collects no information that can identify you, such as your name, email address, phone number, date of birth, or location. There is no sign-up process, and no user account is created on any server. It does not read identifiers such as advertising IDs or unique device IDs either.
2. Information stored on your device
The following is stored only on your device and is never sent off it.
- Study history: progress and review schedules for each card, and daily study amount, accuracy, and study time
- Settings: daily study amount, review limit, target retention, display theme, audio voice and volume, and so on
- Words you save and notes you write
- Downloaded audio files: audio you've played is kept on your device so it isn't downloaded again. If you use “Download all audio”, everything is downloaded at once and takes up about 118 MB.
All of this is deleted when you delete the app. You can also reset it yourself in Settings. Downloaded audio can be deleted separately in Settings → Sound → Download all audio.
3. Network connections
The only place the app connects to is a single storage location for pronunciation audio.
This storage runs on Cloudflare R2 and holds only pre-made audio files.
When you play a pronunciation, the app downloads a pre-made mp3 file. The request URL contains not the word itself but a converted value (hash) of its spelling and reading. Once downloaded, the file is cached on your device and no further connection is made for it.
If you use Settings → Sound → Download all audio, the app downloads a single file containing all the audio. In that case there is only one request, and its URL contains no per-word values at all, so no record of which words you looked up is left on the server. After that, playing audio doesn't use the internet.
In the course of internet communication, general access logs such as IP addresses may be recorded on the server involved (Cloudflare). These are generated automatically by every internet request, and the app does not separately collect them or link them to you.
If an audio file can't be downloaded (for example, when offline), the device's built-in speech engine reads the word instead. In that case, the word's reading is passed to the operating system's speech feature, and how it is handled depends on your device and operating system settings.
4. Permissions
| Internet | Downloading pronunciation audio files |
|---|---|
| Storage read/write | Exporting and importing backup files (only files you choose) |
| Audio settings and vibration | Playing audio and on-screen feedback |
The app does not ask for access to your microphone, camera, location, contacts, or photo library.
5. Ads, analytics, and third-party sharing
The app has no ads and includes no usage analytics or tracking tools. Since it collects no personal information, there is nothing to share with or sell to third parties.
6. Backup files
You can export your study history to a file in Settings and import it again. The file is saved wherever you choose; the app does not keep a copy or send it anywhere. Importing reads only the one file you select and never scans the rest of your storage.
7. Children's privacy
The app is not directed primarily at children, and it collects no personal information regardless of the user's age.
8. Your rights
Since no personal information is collected, there is nothing to request access to, correct, or delete. You can erase the study history stored on your device at any time by resetting it yourself in Settings or by deleting the app.
9. Website
The website shows the same vocabulary as the app in your browser. There is no sign-up or login, and no ads. We use Google Analytics 4 for visit statistics, and we set no other cookies of our own.
- Your card grades and display settings (theme and sound) stay only in your browser's local storage and are never sent to a server. They disappear when you clear your browser data and do not sync with the app.
- A shuffled list order is kept only in session storage, which is cleared when you close the tab.
- Search runs inside your browser, so your search terms are never sent to a server.
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Visit statistics: Google Analytics 4 sets
_gacookies in your browser and sends page views, referral sources, device and browser type, and approximate region to Google. Google does not store IP addresses, there is no personally identifying information such as names or email addresses to begin with, and the data is not used for advertising. You can turn it off with your browser's tracking protection or cookie blocking, or with a browser add-on that blocks Google Analytics. - Pronunciation works by downloading the same pre-made audio files as the app. The request URL contains not the word itself but a converted value (hash) of its spelling and reading, and a downloaded file is cached in your browser. If a file can't be downloaded, your browser's built-in speech feature reads the word instead, and how it is handled depends on your device and browser settings.
- When you open a page, general access logs such as IP addresses may be recorded on the hosting server (Cloudflare). As with the app, we do not separately collect them or link them to you.
- Once you follow a link to the App Store or Google Play, that store's privacy policy applies.
10. Changes to this policy
If this policy changes, the updated policy and its effective date will be posted on this page.