Privacy Policy
Last updated: 2026-10-19
Prefix Phone (the “Service”) is a phone app used as the default phone app on Android. When you place a call, it automatically adds the number of the discount calling service you have set up (the “prefix number”).
This policy explains what data the Service handles and which data leaves your device. Most data, such as your call history and contacts, is handled only on your device and is not sent to our servers.
1. Account
- You can use the Service without registering a name, email address or phone number
- When you first open the app, we issue an anonymous user ID for each device (Firebase Authentication anonymous sign-in). “User ID” below refers to this anonymous ID
- If you uninstall the app, this user ID is lost from your device and cannot be restored
2. Data handled only on your device
The Service reads and writes the following data on your device to provide its features, but does not send it to our servers or to any third party.
| Data | How it is used |
|---|---|
| Call history (call log) | Showing history, calling back, deleting history |
| Contacts | Showing and searching contacts, calling, showing names for incoming calls. Contacts are added, starred or given a default number only when you do so |
| Readings of contact names | Readings are generated and stored on your device so that names written in kanji can be searched by reading |
| SIM and phone number information | Switching prefix numbers per SIM, showing which SIM received a call |
| Settings (prefix number per SIM, rules per contact, bookmarks, display settings, etc.) | Running the app |
| Blocked numbers | Stored in your device’s block list |
| Records of calls placed from other apps (the number, the number actually dialed, the prefix added, date and time) | Showing history. Up to 90 days and 500 entries are kept on your device |
| Numbers for which we have asked for a rating | To avoid asking about the same number twice |
- The Service does not record or listen to call audio
- The Service does not collect location information
- This data may be included in your Google account backup through Android’s device backup feature (backups are managed by Google and we cannot see them)
3. Data sent off your device
Data you send
| Data | Purpose | Retention |
|---|---|---|
| Number ratings (the rated number, “glad I answered” or “unwanted”, optional text, user ID, date and time) | Detecting unwanted calls, providing information about numbers (Section 5) | Until you ask us to delete it |
| Inquiries (category, message, user ID, app version, OS version, platform (such as Android), app language) | Support | One year after the last message |
Data sent automatically
| Data | Purpose | Retention |
|---|---|---|
| Device token for push notifications, app language | Notifying you of replies to inquiries | While the user ID is in use |
| When you last viewed notices | Showing the number of unread notices | While the user ID is in use |
| The caller’s number during an incoming call (only when it is not in your contacts) | Showing Google search results on the incoming call screen (Section 6) | Subject to Google’s privacy policy |
| Usage data (user ID, progress through the introduction, whether you set the app as the default phone app) | Improving the Service | Subject to the retention policies of the third-party services in Section 8 |
| Error information (including user ID, app and OS version, device model, and screen interactions just before the error) | Detecting and fixing bugs | Subject to the retention policies of the third-party services in Section 8 |
| A per-device ID and app version for checking for updates | Delivering app updates | Not stored (used only to choose which update to deliver) |
| Information verifying the app and device | Preventing unauthorized access | Subject to the retention policies of the third-party services in Section 8 |
- Shop names for incoming calls are looked up in a list of shops stored on your device. The numbers you call or that call you are not sent to our servers to look up shop names
- The list of shops (created by us from Overture Maps Foundation data) and the dictionary of name readings are downloaded from our distribution servers. No information identifying you is sent when downloading them
4. Purposes of use
We use the collected data only for the following purposes:
- Providing and maintaining the Service (calls, history, contacts, call blocking, shop names, push notifications, notices)
- Detecting unwanted calls and providing information about numbers (Section 5)
- Responding to inquiries
- Investigating bugs and improving the Service
- Complying with legal obligations
5. Number ratings
- After you talk for 10 seconds or more with a number not in your contacts, we may ask whether you were glad you answered or whether the call was unwanted. We ask only once per number. You can use the Service without answering
- When you send a rating, the rated number, the rating, any text you wrote, your user ID and the date and time are stored on our servers. Rating the same number again replaces your previous rating
- If you send “unwanted”, the number is also added to your device’s block list (you can remove it in settings or from the number’s details)
- Ratings are not currently shown to other users. We use ratings for the following purposes:
- Detecting unwanted calls in the Service and letting users know
- Publishing web pages that combine information and ratings for the phone numbers of shops and businesses. Only numbers of shops and businesses are published; personal mobile numbers are not. When publishing, we do not show user IDs, and we remove information that could identify a person, such as personal names, from the text
- Please do not include information that could identify a person, such as names, addresses or phone numbers, in your rating text
6. Search during incoming calls
- While a call from a number not in your contacts is ringing, the incoming call screen shows Google search results for that number. The caller’s number is sent to Google when this happens
- The search screen opens in a private mode that does not leave browsing history or cookies on your device. We do not read the search results
- When you tap “Search the web” in a number’s details, the number is likewise sent to Google
- Google’s handling of this data is subject to Google’s privacy policy
7. Handling of inquiries
- To understand your inquiry, we translate the message into Japanese using Google’s translation service and store the translation
- To respond, we send the content of the inquiry (message, translation, user ID, app and OS version) to our private task management (GitHub) and our internal notifications (Discord)
- We notify you of our replies by push notification. Even if notifications are not allowed, you can read replies on the inquiries screen in the app
8. Third-party services
To provide the Service, information is sent from your device or our servers to the following third-party services, to the extent necessary.
| Service | Provider | Data sent | Purpose |
|---|---|---|---|
| Firebase Authentication | Anonymous user ID | Identifying users | |
| Cloud Firestore | Number ratings, inquiries, push notification device token, when you last viewed notices | Data storage | |
| Cloud Functions for Firebase | Number ratings, inquiries | Server processing | |
| Firebase Cloud Messaging | Device token, notification content | Push notifications | |
| Firebase App Check (Play Integrity) | Information verifying the app and device | Preventing unauthorized access | |
| Firebase Remote Config | App version, etc. | Delivering feature settings | |
| Google Analytics for Firebase | Usage data (including user ID) | Improving the Service | |
| Google Search | The caller’s number during an incoming call (Section 6) | Showing search results on the incoming call screen | |
| Cloud Translation | Inquiry messages | Translation so we can understand inquiries | |
| Sentry | Functional Software, Inc. | Error information (including user ID) | Detecting bugs |
| Cloudflare | Cloudflare, Inc. | Download requests for the shop list, the name reading dictionary and app updates (update checks include the per-device ID) | Delivering files and app updates |
| GitHub | GitHub, Inc. | Inquiry content | Managing our responses |
| Discord | Discord Inc. | Inquiry content | Internal notifications |
Please see each provider’s website for its privacy policy.
When you open the website of a discount calling service or other site from the Service, that site’s privacy policy applies.
9. Advertising and tracking
- The Service does not show ads
- The Service does not collect the advertising ID (Android advertising ID)
- We do not sell collected data, and we do not provide it to third parties for purposes other than those in Section 8 (except as required by law)
10. Data storage location
- Data on our servers is stored on Google Cloud (Firebase) servers located in the United States
- Google takes measures to protect personal information
11. Data retention and deletion
- Data on your device (Section 2) is removed from the device when you uninstall the app. Call history, contacts and the block list are data held by the device’s OS, so they remain after you uninstall the app
- Number ratings are kept until you ask us to delete them
- Inquiries are deleted one year after the last message
- The Service has no account deletion screen. If you want us to delete your data on our servers (number ratings, inquiries, push notification device token), please contact us through the inquiry screen in the app. Uninstalling the app loses your user ID, after which we cannot confirm which data is yours, so please send deletion requests before uninstalling the app
- We may keep data until the relevant process ends, to the extent necessary to respond to legal requests or resolve disputes
12. Your rights
You can exercise the following rights by contacting us through the inquiry screen in the app.
- Right of access: to request disclosure of your data
- Right to erasure: to request deletion of your data (including ratings shown on published pages)
- Right to rectification: to request correction of your data
13. Additional information for EU users (GDPR)
The following additionally applies to users located in the EU/EEA:
- Legal basis for processing: performance of the contract to provide the Service, and our legitimate interests in improving the Service and preventing abuse
- Data portability: the right to receive your data in a structured, machine-readable format
- Right to object: the right to object to processing based on legitimate interests
- Right to lodge a complaint: the right to lodge a complaint with a data protection supervisory authority
14. Children’s privacy
The Service is not directed at children under 13. We do not knowingly collect data from children under 13. If we learn that data from a child under 13 has been collected, we will delete it promptly.
15. Changes to this policy
- When we change this policy, we will update the “Last updated” date and post it on this page
- When we make changes that affect users, such as the following, we will also notify you in the app:
- Increasing the types of data sent off your device
- Adding or changing purposes of use
- Extending retention periods
- Newly providing data to third parties
- For changes that do not alter how data is handled, such as wording fixes or clarifications, updating this page serves as notice
16. Contact
For inquiries about the handling of personal information, please contact us through the inquiry screen in the app or at the email address below.
Email: support@beruk.co