A corrupted SD card is not an empty one — here's the safe way back

'You need to format this card' — translated

Translate the error before acting on it. Your camera or computer is reporting that the card's table of contents — the file system — no longer parses, so nothing can be found. It is not reporting that the photos are gone: in the flash memory itself they're nearly always whole, filed one layer down from the index that broke. The cruel part of the design is the single button the message offers, because pressing it starts overwriting precisely the material a recovery is rebuilt from.

A format never mends an index — it lays a blank one over the top. A quick format takes seconds to destroy the folder tree, the filenames and the dates that make your photos findable. However insistent the prompt, if the pictures matter, the format waits.

Five minutes of harmless testing

Suspect the reader before the card: readers are cheap and die young, laptop card slots are the least reliable of the bunch, and a standalone USB reader on a second computer makes the fairest jury. On full-size cards, glance at the little lock slider on the edge — nudged to the locked position, it produces strange refusals, including failure to write or format.

Two outcomes should end the testing at once. If the card mounts but pictures seem missing, retire it immediately and shoot nothing more — new files land on the space your old ones occupy. And if no computer sees it at all, or the capacity reads absurdly small (a 64GB card presenting itself as a few dozen megabytes has a crashed controller), software has nothing to offer: the route from there is chip-level work.

When the format itself fails

Some readers arrive at this page backwards: the card misbehaved, a format looked like the reset button, and the format refused to finish. Three usual causes — the lock slider, a controller that has dropped to read-only as it degrades, or electronics on the way out. The read-only case is quietly the best news on this page, because a card that locks itself often does so with its entire contents still readable.

Whatever you do, don't escalate. Format retries, chkdsk marathons and repair utilities each pile operations onto a controller that is failing precisely because operations have become hard for it. A card in this condition that holds anything you'd miss is a recovery case now, not a repair project.

The route your photos actually take home

At the bench, a corrupted card is read once — every sector, in order — into an image file, and the rebuilding of folders, filenames and video happens on that copy while the card itself sits untouched. Cards that are dead, misreporting capacity or physically snapped (microSDs especially) go a different way: the NAND chip is read directly and its contents reassembled. Either route opens with a free diagnostic, so the verdict and the fixed price arrive before any spending decision does.

Posting could hardly be simpler: tape the card inside a folded piece of stiff card, use a padded envelope, send it tracked. Details sit on the memory card recovery page, or jump straight to the free online diagnostic.