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Put the card in a computer before you format anything
Take the card out and connect it to a computer with a card reader. That one test splits the problem: a card the computer mounts and reads is physically fine, so the fault is the camera's slot, a formatting mismatch, or a compatibility limit. A card the computer cannot see either has failed or is write-protected — and before assuming failure, check the small lock switch on the side, because a loose one can slide to locked as the card enters the slot and produce exactly this symptom.
Applies to: SD, SDHC, SDXC and microSD cards in cameras, action cameras and drones, including SanDisk, Lexar, Samsung and Kingston. Formatting and compatibility guidance is manufacturer-documented; specific menu paths vary by camera and are named where a manufacturer publishes them.
What does the card do elsewhere?
“Card not detected”, “No memory card” and “Insert memory card” all mean the host cannot talk to the card, which is a much broader statement than a dead card. It covers a slid lock switch, dirty contacts, a filesystem the camera does not understand, a capacity the camera predates, and a card that is genuinely finished. The computer test separates the physical from the logical in a minute, and everything below follows from it.
The camera says no card, or won’t write
Is the lock switch slid down?
Check the lockIt works in a computer but not the camera
Is it formatted for what the camera expects?
Reformat itNothing sees it, anywhere
Have you tried a proper card reader?
Test it properlyIt fails only on long or high-quality clips
Is the card fast enough for the camera?
Check card speed1. The lock switch, including the one that moves on its own
Full-size SD cards have a small sliding switch on the left edge, and SanDisk's guidance is to make sure it is slid up to the unlocked position — content cannot be added or changed while it is down. This is the single most common cause and it is worth checking even when you are certain you never touched it, because the switch is small, it protrudes, and it catches on the edge of a slot or a pocket.
There is a version of this that is genuinely invisible, and it is the most useful thing on this page. SanDisk notes that if the lock switch is loose and moves easily, it may be sliding into the locked position as the card is placed into the device — so the card looks unlocked in your hand and is locked by the time it seats. Push the switch firmly to unlocked and see whether it holds. If it moves under light finger pressure, the card needs replacing regardless of whether the memory is healthy, because it will keep doing this.
microSD cards have no lock switch of their own, so if you are using one in a full-size adapter, the switch belongs to the adapter and the same rules apply. SanDisk's advice is stronger than that though: microSD adapters should not be used, and a card reader is the right tool instead. Adapters add a mechanical connection and a lock switch that can both fail while the card is perfectly fine.
A locked card often still reads. If the camera can play back existing photos but refuses to take new ones, or reports the card as protected rather than missing, the lock switch is almost certainly the answer.
2. Contacts, debris and how the card is seated
Before touching any software, deal with the physical connection. SanDisk's steps are to make sure there is no debris in the slot, to avoid forcing the card if it feels too tight, and to insert and remove the card a few times — that last one wipes the contacts against the slot's pins and clears light oxidation or dust, which is a real fix and not superstition.
Check the card is not too loose in the slot as well. A slot whose retention spring has weakened lets the card sit slightly proud, so it makes contact intermittently — the camera sees it sometimes, loses it mid-recording, and reports it missing at the worst moment. If the card does not click positively into place, or falls out when the camera is tilted, that is the slot rather than the card.
Inspect the gold contacts on the card itself in good light. Scratches, discolouration or residue all interfere, and a dry lint-free cloth is the only thing that should touch them — no liquids and nothing abrasive. Then power the host device off completely with the card removed and back on before reinserting, which SanDisk lists as a step and which clears a stale mount state that keeps reporting the old result.
3. The computer test decides everything
Connect the card to a computer using a proper card reader rather than an adapter, and see what happens. SanDisk's instruction is to check that Windows assigns a drive letter, and the equivalent on a Mac is whether the volume appears in Finder or in Disk Utility. Disk Utility is worth opening specifically, because a card that appears there but not in Finder is present and readable at the hardware level with a filesystem the Mac will not mount — which is a formatting problem, not a dead card.
A card the computer mounts and reads is physically working. That moves the whole investigation to the camera side: the slot, the filesystem, or a compatibility limit, all covered below. It also means your photos are recoverable, so copy everything off before you do anything else — that opportunity disappears the moment you format.
A card that no computer sees, through a known-good reader, on more than one machine, has failed. That is a legitimate conclusion rather than giving up, and SanDisk's own guidance at that point is a warranty replacement — memory cards typically carry long warranties, often lifetime on the higher tiers, so check before buying a replacement.
Test the reader too. A cheap USB card reader that has been in a drawer for years is itself a common point of failure, and blaming the card for a dead reader is an easy mistake.
4. Where to format, and why the answer changes
There are two pieces of manufacturer guidance here that look contradictory and are not, and knowing which applies saves a lot of confusion. The general rule is to format in the host device: the camera writes a filesystem laid out the way it expects, with its own directory structure and cluster size. That is the right operation for routine maintenance and for preparing a new card.
The exception is a card the device cannot properly read in the first place, and GoPro documents it explicitly for its NO SD error: format the card on a computer, using a card reader, before it can be used in the camera again. A camera cannot rebuild a filesystem it cannot mount, so the computer does the structural repair and the camera can then take over. If in-camera formatting is greyed out or fails, that is the situation you are in.
Match the filesystem to the camera, which is where older bodies catch people out. SanDisk's guidance is to format with a file system supported by the host. In practice SDHC cards up to 32 GB use FAT32 and SDXC cards of 64 GB and above use exFAT, and a camera that predates SDXC will not read an exFAT card at all no matter how it is formatted. Formatting a 128 GB card as FAT32 on a computer to force compatibility is possible but generally a bad idea — the camera is telling you it was designed for smaller cards.
Routine format
In the camera. It writes the directory structure and cluster size the camera expects.
Card the camera won’t read
On a computer with a card reader first, then use the camera normally — GoPro documents this for NO SD.
5. Not detected, or just not fast enough?
Some card errors are not about detection at all but about throughput, and they masquerade convincingly. GoPro publishes a test that separates the two and it works on any camera: format the card, then record two clips — one at a low resolution and frame rate, one at high. An error that appears only on the high-performance recording means the card cannot keep up with the camera's output. An error on both points at the card or the firmware.
That distinction matters because the fixes are unrelated. A card that is too slow is not faulty and will not be improved by formatting or by cleaning contacts — it needs replacing with one that meets the camera's speed requirement. Manufacturers publish recommended card lists for exactly this reason, and 4K and high-frame-rate video is where a card that was fine for stills starts failing.
Read the speed markings rather than the headline number on the front. The class rating inside the U symbol, the V rating for video, and the A rating for application performance describe sustained write speed, which is what matters here; the large megabytes-per-second figure on the packaging is usually a peak read speed and tells you very little about whether a camera can record to it reliably.
6. Compatibility, and what to tell support
Check the card against the camera's supported list before concluding anything is broken. SanDisk's guidance is to consult the host device manufacturer's supported memory card list and the device manual to confirm compatibility, and this catches a specific and frustrating case: a camera that predates a card standard will not recognise a card that is otherwise perfect. An SDXC card in an SDHC-era body, or a very high capacity card in an older drone, simply will not be seen.
If one card works and another does not in the same camera, that is conclusive and useful — the slot and the camera are fine, and the difference is the card's capacity, filesystem or speed. GoPro's own guidance for a persistent problem is to try a secondary card to narrow down whether the fault is the card or the camera recognising cards, and it is the fastest way to reach an answer.
When you contact support, lead with the computer test. Tell them whether a computer with a card reader can see the card and assign it a drive letter, whether the lock switch is unlocked and holds firmly, whether a second card works in the same camera, whether the card works in a second camera, and whether the error appears on all recordings or only high-quality ones. Those five answers separate a locked card from a dead card from a slot fault from a card that is simply too slow.
Frequently asked questions
Why does my camera say no memory card when there is one in it?
Check the lock switch on the card's left edge first — SanDisk's guidance is to slide it up to unlocked. Then test the card in a computer with a card reader. If the computer reads it, the card is physically fine and the fault is the camera's slot, the filesystem, or a compatibility limit. If nothing reads it anywhere, the card has probably failed.
My SD card lock switch is unlocked but it still won’t write. Why?
The switch may be sliding on its own. SanDisk notes that a loose lock switch can move into the locked position as the card is inserted, so it looks unlocked in your hand and is locked once seated. Push it firmly to unlocked and see whether it holds — if it moves under light pressure, the card needs replacing even though the memory itself is healthy.
Should I format my SD card in the camera or on a computer?
In the camera for routine formatting — it writes the directory structure and cluster size the camera expects. On a computer only when the camera can't properly read the card in the first place: GoPro documents formatting on a computer with a card reader before the card can be used in the camera again. A camera can't rebuild a filesystem it can't mount.
Can I use a microSD adapter instead of a card reader?
SanDisk advises against it — the guidance is that microSD adapters should not be used and a card reader is the right tool. An adapter adds a mechanical connection and its own lock switch, and both can fail while the card itself is perfectly healthy. If you're diagnosing a card, an adapter adds a variable you don't want.
Why does my card only fail when recording 4K?
That's a speed problem, not a detection one. GoPro's test works on any camera: format the card, then record one clip at low resolution and frame rate and one at high. An error only on the high-quality clip means the card can't sustain the camera's write rate. Check the V and U speed markings rather than the headline megabytes-per-second figure, which is usually peak read speed.
Why won’t my old camera read a new high-capacity card?
Because it probably predates the standard. Cards of 64 GB and above are SDXC and use exFAT, and a camera built for SDHC won't read them at all regardless of formatting. SanDisk's advice is to check the manufacturer's supported card list and the device manual. If a smaller card works in the same camera, that confirms it — the slot is fine and the capacity is the limit.
Sources and review notes
Checked on . Compiled by Glitchary from SanDisk and GoPro support documentation. Card compatibility, capacity limits and formatting menus vary by camera — check your camera manufacturer’s supported card list before concluding a card has failed. Guidance on speed class markings and filesystem capacity thresholds reflects the SD standard rather than a single vendor’s documentation. Glitchary is independent of SanDisk, Western Digital and GoPro.
- SanDisk: resolve a microSD or SD memory card not detected, or an insert memory card message
- SanDisk: solutions to a write protected, read-only or locked microSD memory card
- SanDisk: how to unlock a write protected, read-only or locked SD card
- SanDisk: formatting a memory card, flash drive or device using a PC
- GoPro: NO SD or SD ERR camera error