Dual N-Back: Privacy Policy

Effective 7 November 2026. Published at https://apps.digitalshijil.com/dual-n-back-trainer/privacy/

Dual N-Back ("the app") is published by DIGITAL SHIJIL LLC. Questions: contact@digitalshijil.com.

The short version

Your rounds, levels and settings are stored on your phone only. The app has no account, no ads, no analytics, no backend and no network code of its own. The only data that leaves the device is the diagnostic logging that Google's Play Billing library sends to Google when the app talks to Google Play about the Pro purchase.

What the app stores on your phone

• Rounds: for each finished round, the date and time, the mode, the level, the number of trials, the time per trial, and the hits, misses and false taps for each stream (position, letter, color).
• Custom modes you create: the name and the rules you chose.
• Settings and levels: the level you reached in each mode, round length and speed, how letters are given (spoken, shown or both), whether feedback after each trial is on, light or dark appearance, and when you last saved a copy.

This data lives in the app's private storage. The publisher never receives it and cannot see it.

Spoken letters

Letters are spoken by the text-to-speech engine that is already installed on your phone, one letter at a time. The app does not record audio and does not use the microphone. Which engine speaks, and whether it works offline, depends on your phone and the engine's own settings; their privacy terms are the engine maker's. If you choose "Shown only", no speech engine is used.

Purchases and Google Play

Pro is sold by Google Play as a yearly subscription (with a free trial) or a one-time lifetime purchase. The app never sees your payment details. To check and restore the purchase, the app uses the Google Play Billing library, which exchanges purchase information with Google Play and sends Google diagnostic logs about the billing connection (Data safety: App info and performance > Diagnostics: collected, not shared, required). That logging is controlled by Google under the Google Privacy Policy: https://policies.google.com/privacy

Permissions

• The app asks for no permission of its own: no internet, notifications, camera, microphone, storage, media, contacts or location.
• The only permission in the release build is the Play Billing permission added by the billing library.

What the app does not do

• No account, sign-in or registration.
• No advertising, no advertising ID, no analytics and no crash-reporting SDK.
• No upload of your rounds or settings, ever.
• No selling or sharing of your data with anyone.

Exports, backups and sharing

• "Export all my data" (JSON) and the history CSV (Pro) are created on the phone and shared only when you choose an app in Android's share sheet.
• A backup file (optionally protected with a password you choose) is written to a place you choose with the system file picker.
• If you use Android's own device backup, Android may include the app's data under your Google account's backup settings. The purchase cache is excluded from it.

Deleting your data

Settings > Delete all data erases the rounds, custom modes and every setting on the device. Uninstalling the app also removes everything it stored. A Pro purchase stays with your Google account and is restored by Google Play. If a subscription ends, nothing is deleted: your history stays on the phone, can be viewed and can be exported as JSON.

What the app is

Dual N-Back is a game for keeping track of your own practice. It is not a medical, educational or testing product and it makes no promise about results.

Children

The app is not directed at children under 13 and is not designed for them.

Changes

If this policy changes, the new version is published at the address above with a new effective date before the change ships in the app.

Contact

DIGITAL SHIJIL LLC, contact@digitalshijil.com