How Android works

Storage

From the wild west of /sdcard to scoped storage.

5 pages57 min5 interactive8000 words

01The history of Android storageFrom a real SD card that any app could read to a virtualised filesystem with per-app views: how WRITE_EXTERNAL_STORAGE became a privacy disaster, and how Android unwound it.intermediate11 mininteractive
02Scoped storageThe model that replaced the free-for-all: app-specific directories, MediaStore collections, per-file grants, and the permissions that survived — plus the ones that did not.intermediate12 mininteractive
03The Storage Access FrameworkA picker, a provider interface and a persistent URI grant: how an app gets at a file it does not own without ever learning a path.intermediate11 mininteractive
04App data and databasesPreferences, files, SQLite and their modern replacements: why SharedPreferences and SQLite are still there, what DataStore and Room fixed, and what survives a backup, a reinstall and a device transfer.intermediate12 mininteractive
05vold and filesystemsThe volume daemon, the filesystems it mounts, adoptable storage, encryption and the 16 KB page change — the layer under /data that almost nobody sees.nerd11 mininteractive

Test yourself

Test yourself: Storage

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What does ACTION_OPEN_DOCUMENT_TREE give an app that ACTION_OPEN_DOCUMENT does not?