SD Card Won't Format or Delete Files: Is It Stuck Read-Only?
If files reappear after deletion and both formatting and repair attempts fail, the card may no longer be accepting writes. In this r/datarecovery case, a 512GB SanDisk Ultra microSDXC on Windows 11 would not format with the official SD tool or guiformat, CHKDSK did not change the state, and deleted files remained visible. The user had already backed everything up and only wanted the family photos removed before a warranty return.
Do Not Assume a Successful Delete Message Means the Data Is Gone
If the files reappear after reconnecting the card, treat the erase as unsuccessful. For a privacy-sensitive return, you need a write that actually changes the media, not just a file-manager confirmation.
Could This Just Be a Write-Protect Switch?
A microSD card itself has no full-size SD lock tab, but a microSD-to-SD adapter can. The SD Association recommends checking that the write-protect switch is in the unlocked position before formatting. If an adapter is involved, check it once or try another known-good reader. If the card still refuses every write, stop treating this as a simple adapter-lock problem.
Why Can a Failing Card Become Read-Only?
SanDisk documents that a memory card can place itself into write protection when too many storage blocks have failed or when critical block copies are corrupted. That behavior is meant to preserve readable data, but it also means normal delete and format commands may no longer change the flash.
Can You Safely Erase It Before Returning It?
Use the Result, Not More Formatting Attempts
- A different known-good adapter or reader restores normal writes: use the SD Association formatter and verify afterward that the old files no longer return.
- The card remains read-only and old files keep reappearing: software erasure is not trustworthy. NIST SP 800-88 Rev. 2 notes that overwriting cannot sanitize media that is too damaged to be reliably rewritten, and flash storage can also retain data outside directly addressable areas.
- The files are private and you cannot verify sanitization: contact SanDisk before the RMA and explain that the failed card cannot be erased. If the return process still requires sending the original media, decide whether the warranty value is worth giving up physical control of a card that may still contain readable family photos.
Because the data is already backed up, there is no reason to keep running CHKDSK, alternate formatters, or recovery software. The decision is now about sanitization: either verify that writes work and erase the card successfully, or treat the card as unsanitized media and keep physical control of it.