Privacy Policy

2026-11-06

This policy explains how the operator of Sudoku AI Coach ("the app") handles your information.

1. Information we collect and how we use it

Device ID

When you first open the app, it creates a random ID for your device. It is not linked to your name or phone number. We use it to manage your daily AI coach questions, rankings, feedback, and linking to an account.

Rankings

When you clear a puzzle, the app sends the record of the clear (the puzzle, time taken, number of hints, score, and the order and timing of your entries) to our server and shows it on the world ranking. If you have not entered a nickname, a short ID derived from your device ID (for example, k7m2qa) is used as your name. If you enter a nickname, country or region, the app sends those too (choosing a country/region also enters you in the national and regional rankings). The app also sends the app version, OS name, the region of your device's language setting (for example, JP) and "where you came from" described below (only if anonymous usage data is turned on). We use this to show rankings and to detect invalid records and records from test devices. Your nickname (or short ID), short ID, country/region and score are shown to other players (the app version, OS, language region and where you came from are not shown).

If you report another player's nickname, the short IDs of you and that player and the nickname are sent to the operator. Nicknames reported by several players are no longer shown. Your list of blocked players is stored only on your device.

Location (optional)

Only when you choose "set from current location" for your ranking country/region, the app uses your approximate location. Converting it into a country/region is done by your device's operating system, and your location itself is not sent to our server.

Questions to the AI coach

When you ask the AI coach a question, the question and the content of the hint on screen (the explanation of the solving steps) are sent to our AI provider (Anthropic, PBC) to generate an answer. Our server does not store your questions except to count how many you have used. Your conversation history is stored on your device (and in your backup if you create an account).

Feedback

When you send feedback from the settings, we store its content together with part of your device ID, your OS, app version and language, and deliver it to the operator by email. There is no reply function.

Error and crash reports

When an error or crash happens in the app, it sends the error details (message and stack trace), app version and build number, OS name and version, device language and your device ID to our server so we can find and fix the problem. Reports do not include your board, email address or the text of your questions. If something like an email address or ID slips into a report, our server removes it before recording. Reports are stored in Amazon Web Services (CloudWatch) and the operator is notified.

Anonymous usage data (you can turn this off in Settings)

To improve the app (to learn whether people keep playing, which screens and features are used, and where people stop), the app (including the browser version) sends anonymous usage events to our server. These are fixed items only: opening and closing the app (days since install, time spent), screens opened (with the previous screen and how many seconds were spent there), starting, clearing or leaving a puzzle (difficulty, whether it is the daily puzzle, a rough time range, number of hints and mistakes, roughly how much was filled in, and how many times actions such as undo, erase and notes were used), whether hints, ads and the AI coach were used (counts and result types only), changes to the language or settings, how long the app took to start, failed connections to our server (which feature, the status code and a rough time range), and where you came from when you first opened the app (in the browser version, the name of the site you were on just before (or, for pages on this site, which page), utm parameters in the URL and the first screen opened; on Android, the referrer reported by Google Play), together with the app version, OS name and version, display language and the region of your device's language setting (for example, JP). We do not send your board, the text of your questions, your email address or your advertising ID. Your device ID is turned into a one-way value on our server before it is recorded, and it is not linked to rankings or accounts. Records are stored in Amazon Web Services (CloudWatch), and the operator only looks at aggregated numbers (such as the number of users and retention). The app does not use third-party analytics services. If you turn off "Share anonymous usage data" in Settings, events waiting on your device are deleted and nothing more is sent (this is separate from ad consent).

Account (email verification, optional)

The email address you enter to create an account is used only to send a verification code and is not stored on our server (we store only a one-way value derived from it to recognize the same account). Emails are sent using Amazon Web Services. With an account, the app stores your records, settings, AI coach conversations and similar data on our server so you can restore them on another device. You can delete your account at any time from the Me tab; deleting it removes your backup and ranking records from our server. See Delete your account and data for details.

Website analytics (Google Analytics)

Our website (puzzlecoach.app) uses Google Analytics to learn which pages are read and where visitors come from. Google Analytics uses cookies, and Google collects information such as the pages you open, the site you came from, your browser and device type, and your approximate region. We do not send information that identifies you, such as your name or email address. The information is handled under Google's privacy policy, and user-level data is deleted after 2 months. In the European Economic Area, the UK, and Switzerland, cookies are not used until you consent. See How Google uses information from sites or apps that use its services for details. You can stop collection with the Google Analytics Opt-out Browser Add-on.

Advertising

The app shows ads provided by Google AdMob. Google may collect and use information such as your advertising ID to deliver and measure ads. See Google's advertising policies for details. In the European Economic Area and similar regions, the app asks for your consent before showing ads. On iPhone, the app asks for permission to track (personalize ads across apps) before showing ads; the app works the same if you decline. You can reset or disable your advertising ID in your device settings.

The website (puzzlecoach.app) and the browser version may show ads provided by Google AdSense. Third-party vendors, including Google, use cookies to serve ads based on your prior visits to this website or other websites. Google's use of advertising cookies enables it and its partners to serve ads based on your visits to this site and/or other sites on the internet. You can opt out of personalized advertising in Ads Settings (you can also opt out of some third-party vendors' cookies at www.aboutads.info). In the European Economic Area, the UK, and Switzerland, we ask for your consent before showing ads.

2. Sharing with third parties

Except where required by law, we do not share your information with third parties for purposes other than those above. Information is sent to the AI provider, Amazon Web Services and Google only as needed for the purposes described.

3. Retention

Weekly and monthly ranking records are deleted after each period ends. Feedback is deleted after 30 days and verification codes after 10 minutes. Error/crash reports, anonymous usage data and access logs are deleted after 90 days. Account backups are kept while you use the account.

If you can't use the app or can't log in, email info@chordup.io and we will delete your data within 30 days. See Delete your account and data for how.

4. Children

The app is not directed at any particular age group. Users under 13 should use it with a parent's or guardian's consent.

5. Changes

If we change this policy, we will post the update on this page.

6. Contact

Please contact us from the app (Me tab → Settings → "Send feedback") or by email at info@chordup.io.