Callback collects no data whatsoever.
Nothing. Callback has no accounts, no sign-in, no analytics, no advertising, no crash reporting, and no third-party SDKs.
Callback makes no network requests. All lessons and questions ship inside the app; every feature works with the device in airplane mode.
Your study progress — answers, mastery scores, streaks, saved topics, and session history — is stored only on your device. It is never transmitted anywhere. You can export it as a JSON file from the Profile tab, and you can erase it at any time via Profile → Reset all data, or by deleting the app.
Callback is rated 4+ and contains no objectionable content, no user-generated content, and no communication features.
If this policy ever changes, the revised version will be posted on this page.
Questions: babin@axveer.com