using your external SD card as internal storage with Android 6+

What is "adoptable storage"?

Adoptable Storage was introduced with Android Marshmallow () to address the permanent issues with too low internal storage (especially on budget devices — see ) by "adopting" external storage to substitute for the internal storage.

If your device supports external SD cards and runs on Android 6.0 or higher, on insertion of a card you will be asked whether to use it as "portable storage" (i.e., the same way you've used it before), or if Android should adopt it as "internal storage":

setup USB drive
Screenshot (click image for larger variant)

What happens behind the scenes?

If you chose to "adopt" external storage as internal storage, it will be encrypted. Which means multiple things:

  • this storage can only be used in the device it was "encrypted into"1
  • you no longer can simply switch it to another device: lacking the encryption key, it will be unreadable there
  • you no longer can use a card reader to access the card's content in case your battery run out (or your device gets damaged), to rescue some data
  • no "simple upgrade" to another (bigger, healthier, faster) SD card
  • all data on the card will be erased while "initializing the adoption". Same applies if you want to revert the process.
  • whatever real internal storage you had will become invisible to both and normal (non-root) file management apps, and even then, it can only be accessed with considerable difficulty as a mounted storage.
  • when you your device, you cannot even use recovery software to rescue data from the card (as the encryption key will be gone as well).

Further readings:


1: Basically. There are ways around this. See Corrupt SD card formatted as internal storage or Decrypting Android M adopted storage for examples

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