In the device's own words
Whatever it is saying, start here. The message is the device's. The data is yours.
A memory card has no screen of its own, so the message comes from whatever it is plugged into, and each device words the same handful of faults its own way. Windows asks you to format the disk; a Mac says the disk was not readable; Android says the card is corrupted; a Canon says Err 02 and offers to format it for you; a GoPro says SD ERR; a Switch says 2016-0247. Behind nearly all of them is one of three things: file tables the device cannot read, a controller that has stopped answering, or a card that has worn out and locked itself. And nearly all of them come with a button that makes it worse, because the device's fix for a card it cannot read is to wipe it and start again. Each page below quotes the message, says what is behind it, names the button to leave alone, and says which band it falls in. A card a reader still sees is £149 + VAT after the free look, fixed in writing; a card none sees, or one snapped, locked or lying about its size, is £299 + VAT.
Rather talk it through? An engineer answers the bench line
0800 6890668
What the computer says, or what the device says.
Rather begin with the card →What the computer says
You need to format the disk before you can use itWindows cannot read the file tables. The photographs are still there. Say no, and why a quick format differs from a full one→Card not recognised, or not showing upThe reader, the adapter, the slot, or the card's controller. How to tell which in two minutes, and when it is monolith work→Windows was unable to complete the formatThe card refused the write: locked read-only, worn out, or a fake. The good news is that the format failed→The disk is write-protected, or read-onlyThe switch, the adapter, or the card's own end-of-life lock, in SanDisk's words. Copy everything off now→RAW, 0 bytes, or the wrong capacityAn unreadable file system, a controller that lost its table, or a card that was never the size on the label→Mac: the disk you inserted was not readableInitialize, Ignore or Eject: which to press, why First Aid writes, and the ext4 card a Mac will not show→What the device says, or what happened
Android: SD card is corrupted, or unsupportedPortable storage with damaged tables, or an adopted card encrypted to the phone. Android's own words on which can be read→Canon Err 02: card cannot be accessedCanon's wording and its format offer. What the camera is telling you, and what Nikon, Sony and Fujifilm say instead→GoPro SD ERR and NO SDGoPro's page, quoted: back up before the format it suggests. Worn cards, fakes, and clips cut short→Nintendo Switch error 2016-0247Nintendo's note that a formatted card cannot be recovered, and why the album usually can be→Formatted, or deleted by mistakeWhat a quick format leaves, what a full format destroys, what the camera's format does, and why you stop shooting→Snapped, cracked, bent or wetThe die inside a microSD, the shell of an SD card, the pins of a CompactFlash, and salt water→Three faults, a dozen messages, one button.
The first fault is torn file tables. A card is written in two steps, the data and then the entries that point at it, and a battery that dies, a card pulled out, or a phone that crashes between the two leaves tables that no longer describe the data. Every device reports that differently and every device offers the same cure, a format, because the device's job is to make the card usable again and the format does that. It also rewrites the tables, and on a Windows full format writes zeros over everything. The photographs are on the card until that happens. The second fault is a controller that has stopped: the card presents nothing, or presents 0 bytes, or presents a few megabytes where a hundred gigabytes should be. No format will help and none can be run; the flash is read around the controller. The third is wear: a card that has been written to death locks itself read-only and tells you so, and the only right response is to copy everything off before it stops reading as well.
The devices' own documentation is quoted on each page because it is more persuasive than ours. Canon's camera note says all images and data will be erased during reformatting. GoPro's page for SD ERR says to back up any pictures and videos before you proceed. Nintendo's page for 2016-0247 says that once formatted, the information on the card cannot be recovered. SanDisk's support note says a card will write-protect itself when its good blocks fall below a threshold. The SD Association's formatter manual says data after a quick format may be retrieved by using a data recovery tool. Read together, they say what this site says: do not press the button, take the card out, and let the image be made first.
What the message does not tell you is which band you are in, and the free look does. A card a reader still sees with any of these messages is £149 + VAT after the free look; a card none sees, or one snapped, locked and failing, or lying about its size, is £299 + VAT; the PCIe cards, CFexpress, XQD, CFast and SD Express, are SSD work from £449 + VAT. How a memory card is recovered, from the reader to the monolith says what happens on the bench in each case.
The questions that come up first.
Which of these is the worst?
The one that was followed by a yes. A card that needed formatting and was formatted, a card that was repaired by chkdsk or First Aid, a card that was rescanned by a recovery tool with a repair option, each has been written to since the fault. Untouched, nearly every message on this page is the lower band.
Can I try recovery software first?
If the card reads cleanly at its correct capacity and the fault is deleted, formatted or corrupt, yes, on an image rather than the card, and the software page says how. If the card drops out, reads slowly, shows the wrong size or is not seen at all, no.
My message is not here.
Describe it on the form, in the device's words, with a photograph of the screen. An engineer will place it; the first look is free.
Whatever it said, the answer tonight is the same.
Take the card out, say no to the format, and send the form. The first look is free, and the figure is in writing before anything chargeable happens.