The hasFragileUserData flag can be added to the application node of AndroidManifest.xml. If its value is true, then when the user uninstalls the app, a prompt will be shown to the user asking him whether to keep the app's data.
<application
...
android:hasFragileUserData="true" tools:targetApi="q">
...
</application>
This has been moved to https://github.com/agnostic-apollo/Android-Docs/blob/master/en/docs/apps/processes/phantom-cached-and-empty-processes.md
Some important headings are kept so that users can redirect to new link if they land here.
On August 25, 2025 Google published a blog that starting in 2026, Android will require all apps to be registered by verified developers in order to be installed by users on certified Android devices. This applies to all apps installed from outside the Google PlayStore from either third part app stores like F-Droid, or directly from sites via browsers/file manager apps. Publishing apps on Google PlayStore already has had these same requirements since July 12, 2023. The verification requirements for all apps will engage for Brazil, Indonesia, Singapore and Thailand in September 2026 and engage globally in 2027 and beyond.
There has been lot of noise and backlash regarding the new requirements since then. Malware being deployed both outside and from PlayStore is a big issue and is obviously a cause for concern and a legitimate reason for how developer verification can help reduce it,