Home / Blog / Troubleshooting

SD card corrupted, or won't format? Do this before anything else

What 'you need to format this card' actually means

When a camera or computer says the card needs formatting, it isn't reporting that your photos are gone — it's reporting that it can no longer read the card's index (the file system). The photos themselves usually still sit in the card's memory, perfectly intact, one layer below the broken index. That's why this error is so dangerous: the fix the message offers is the one action that starts destroying the evidence.

Formatting rebuilds the index by wiping it. A quick format on a corrupted card overwrites exactly the structures a recovery lab uses to put your photos back together with their names, folders and dates. If the pictures matter, the answer to 'format now?' is always no.

Safe things to try first

Take the card out of the camera and try it in a different reader — card readers fail more often than cards, and the built-in slots on laptops are worse than a decent USB reader. Try a second computer. Check the tiny lock slider on full-size SD cards hasn't slipped to the locked position (it causes bizarre behaviour, including refusal to format or write).

If the card appears but photos look missing, stop using it immediately — don't take 'test shots', don't let your phone or camera write anything. Every new file overwrites deleted or orphaned photos. If the card doesn't appear anywhere at all, or appears as the wrong size (a 64GB card showing as 30MB is a classic failed-controller sign), no software you run can help — that card needs chip-level work.

A card that won't format is telling you something

People often try to 'fix' a misbehaving card by formatting it, and find even the format fails. A card that won't format is usually write-protected (the lock slider, or a controller that has locked itself read-only as it fails) or electrically dying. Ironically this can be good news for recovery: a controller that fails into read-only mode often leaves the data fully readable.

Don't run repeated format attempts, chkdsk loops or 'repair' utilities on a card in this state — a struggling controller needs fewer operations, not more. If the card held anything you care about, treat it as a recovery job, not a repair job.

Getting the photos back

For corrupted cards we image the card sector by sector and rebuild your photos and video from the image — the card itself is never worked on beyond that first read. For dead, wrong-size or physically damaged cards (including snapped microSDs) the memory chip is read directly and reassembled. Either way you'll know what's recoverable before you spend anything: the diagnostic is free and it's no fix, no fee.

A card fits in an envelope — tape it inside a folded piece of card and post it tracked. Details on the memory card recovery page, or start the free online diagnostic now.

The one rule: if the photos matter, never format a card that's asking to be formatted. The error means the index broke — the photos are usually still there underneath it.

// questions on this topic

Common questions

A format wipes the card's index and starts reusing the space, so it makes recovery harder and sometimes impossible. If you need the photos, don't format — have the card imaged and the file system rebuilt instead.
Common causes: the physical lock slider is on, the controller has failed into read-only mode, or the card is electrically failing. If the card ever held photos you need, a failed format is your cue to stop — the data is often still readable at lab level.
That's the card's controller failing and reporting a default capacity. Software can't fix it; the NAND memory has to be read directly and reassembled. The photos are usually still in the chips.
Usually, if the card hasn't been used since. Deleted photos stay in memory until new shots overwrite them — stop shooting on that card and send it in as-is for the free diagnostic.

Need it recovered rather than explained?

Free diagnostic, fixed quote, no fix no fee — start now or call the freephone.