Android SD card set as internal storage won’t read? What to do

Some Android phones let you format a microSD card as internal storage (Android calls this “adoptable storage”; the setting may be labelled “Format as internal” or “Phone storage”). It is a handy way to add space to a phone with little built-in memory, and apps, photos and downloads then save to the card without you noticing. The catch only appears when something goes wrong: the phone breaks, is reset, or the card is moved to another device, and suddenly the card is unreadable. A computer asks to format it, and another phone says it is corrupted or unsupported. This article explains why, and what you can still do.

Why the card cannot be read anywhere else

When Android adopts a card as internal storage, it formats the card with its own layout and encrypts it. The encryption key is not stored on the card. It is kept on the phone that formatted it. That has some important consequences:

• A Windows PC or Mac sees the card as blank, unformatted or RAW and offers to format it. The data is there, but it is encrypted and the computer has no key.
• Another phone will not read it either. It may offer to format or “set up” the card.
• Recovery software on a computer cannot decrypt the card without the key held by the original phone.

In other words, the card and the phone that formatted it now work as a pair. Keep both.

How you got here matters

The phone is broken but was never reset

This is the most hopeful case. A phone with a smashed screen, a dead battery, a charging port fault or liquid damage usually still has the key in its own storage. If the phone can be brought back to a working state, with the same card put back in, the card’s contents normally become readable again and can be copied off. Recovery in this case is mainly about getting the original phone working, not about the card.

The phone was factory reset

A factory reset deletes the phone’s encryption keys, including the one for an adopted card. Without that key, the encrypted contents of the card cannot be decrypted by anyone. Unless the files were backed up or synced somewhere else, a reset phone usually means the data on an adopted card is lost.

You chose “Forget” in storage settings

If an adopted card is missing, Android may offer to “forget” it. Forgetting the card deletes its key from the phone, with the same result as a reset. Do not choose this if you still need the card’s contents.

The card itself has failed

If the original phone still works but reports the card as damaged or does not detect it, the card may have a physical fault. Then both the card and the phone are needed: the card has to be read at a low level, and the data still has to be decrypted with the phone’s key.

What to do now

1. Put the card back in the original phone, if you moved it, and do not use the card in anything else.
2. Check your backups first. Look in Google Photos (photos.google.com) to see whether pictures were backed up, and check Google Drive, Google Contacts and any messaging app backups. On Samsung phones, check Samsung Cloud and OneDrive if they were set up.
3. Keep the phone as it is. Do not reset it, update it repeatedly or let anyone wipe it as part of a repair.
4. Tell the repairer the card is adopted storage. Some phone repairs end with a reset or a board swap. If the main board is replaced, the key goes with the old board.
5. If the phone will not power on, have it assessed for a board-level repair with the aim of getting it running long enough to copy the data.

What not to do

• Do not format the card in a computer, camera or another phone.
• Do not run “repair” or partition tools on the card.
• Do not factory reset the phone or select Forget for the missing card.
• Do not throw away a broken phone because “the photos are on the SD card”. With adopted storage, the phone holds the key.

Avoiding this next time

If you want to swap a card between devices, or keep photos safe when a phone fails, use the card as portable storage instead. It is not encrypted by the phone and can be read in a computer. Whichever setting you use, keep automatic photo backup switched on and copy important files to a computer or cloud service now and then.

Getting help

We recover data from Android phones and from memory cards and other flash media. If your phone used its microSD card as internal storage and has now failed, bring us both the phone and the card. Call 020 7064 4996 or request a quote for a free assessment, with no obligation.