When an SD card fails to read, test a reader, clean contacts, try a device, repair the file system before formatting.
Nothing kills momentum like a memory card that refuses to mount. The good news: most cases come down to connection problems, file-system errors, or mismatched formats. This guide gives step-by-step checks for computers, phones, tablets, and cameras. Start at the top and work down.
Quick Checks That Solve Most Cases
These fast moves clear many card glitches without risking data. Try each one, then retest.
- Remove the card. Power the device off, wait ten seconds, and reinsert.
- Test a second reader or slot. USB hubs can be flaky; plug a reader straight into the computer.
- Inspect the gold pads. If you see smudges, wipe gently with a microfiber cloth or a clean pencil eraser, then blow off debris.
- Flip the write-protect tab on full-size cards a few times, then leave it in the unlocked position.
- Try a different device: another PC, a phone with a tray, or the camera that usually uses the card.
- Use a short, known-good cable with phone readers and combo docks.
Card Type, Size, And Compatibility
Cards have families (SD, SDHC, SDXC, SDUC) and file systems (FAT variants or exFAT). Old devices may mount only smaller families or only FAT32. New devices read exFAT on larger cards. The table below helps you match capacity and format for broad compatibility.
| Family & Typical Size | Default Format | Notes |
|---|---|---|
| SD (up to 2 GB) | FAT12/16 | Works on nearly all legacy readers. |
| SDHC (4–32 GB) | FAT32 | Single file limit 4 GB on FAT32. |
| SDXC (64 GB–2 TB) | exFAT | Use exFAT for modern PCs, phones, and cameras. |
| SDUC (2–128 TB) | exFAT | Newer standard; many devices still gain compatibility. |
If a device expects FAT32 and your card is exFAT, it may refuse to mount. When in doubt, format in the device that will own the card once data is backed up. On computers, the SD Association’s SD Memory Card Formatter picks the right scheme for each family and keeps performance healthy.
Windows: Detect, Repair, And Recover
Confirm The Reader And Letter
Open File Explorer and check “This PC.” If you see a new drive letter or a removable device with no letter, assign one in Disk Management. If the reader never appears, try a new reader or a different port.
Run Error Checks
Right-click the card in File Explorer, choose Properties → Tools → Check. This launches the built-in error checker. Command-line users can run chkdsk X: /f (replace X with the drive letter) to fix logical errors. Large cards can take time; let the scan finish.
Handle RAW Or Unallocated Media
If Disk Management shows RAW or unallocated space, the file system is damaged. Try recovery before you format. If recovery isn’t needed, delete any existing partition on the removable drive and create a new one, then quick-format to FAT32 (up to 32 GB) or exFAT (64 GB and larger).
macOS: Mount, First Aid, And Format
Find The Volume
Open Disk Utility and choose “View → Show All Devices.” Look for the card under External. If it shows but is grayed out, click Mount. If it ejects itself, try another reader.
Run First Aid
Select the volume, then run First Aid. If it passes, try your files again. If warnings mention a failing device, stop and copy off anything you can. When repairs fail cleanly, back up and erase the card with the correct format.
Erase With The Right Scheme
In Disk Utility, pick the top device entry, choose Erase, set Format to exFAT for 64 GB and larger or MS-DOS (FAT) for 32 GB and smaller, and set Scheme to Master Boot Record for best reader compatibility. Then click Erase.
Android: Phone And Tablet Checks
Confirm Recognition
Open Settings → Storage. If the removable storage entry is missing, power the phone off, reseat the tray, and boot again. If the card shows up, tap it and run the built-in check tool if offered.
Portable Vs. Internal Mode
Some models let you format the card as portable storage or as internal storage. Portable keeps files visible across devices. Internal encrypts and binds the card to that phone; other devices won’t read it. Pick portable for cameras and mixed use. Pick internal only when you plan to keep the card in that phone.
When Files Don’t Appear Over USB
Switch the USB mode to “File Transfer (MTP)” after you plug into a computer. If photos or songs still don’t populate, clear media cache, reboot, and wait a few minutes while the index rebuilds. Slow cards can take a while to scan.
Cameras, Drones, And Recorders
Many devices write faster and fail less when the card is prepared in-camera. Use the in-menu format after you back up. If a camera warns about speed class, move to a V30 or better card for 4K video. For long recordings, avoid filling to 100%—leave a little headroom. Always keep batteries charged during long formats.
Data Safety Before You Reformat
Formatting clears directory data. If the files matter, try recovery first. Stop writing to the card, clone it block-for-block to an image, then try recovery on the image. Free tools can copy raw devices on every desktop OS. Paid tools can scan for photos and videos by signature. Success rates drop once new data overwrites old clusters.
Close Variant Keyword: Memory Card Not Detected Fixes
This section bundles the most common symptoms and the fastest proven remedies. Work from left to right: cause, quick fix, deeper fix.
| Symptom | Likely Cause | Fix |
|---|---|---|
| No chime, no mount | Bad reader/cable or dead card | Try a new reader and port; test on another device. |
| Drive shows RAW | File-system damage | Run repair; recover files; reformat if clean repair fails. |
| Visible, no files | Hidden or corrupted index | Run repair; toggle show hidden files; scan for recoverable media. |
| Write error | Lock tab or failing flash | Unlock tab; back up; replace if errors return. |
| Camera says “reinsert” | Dirty pads or format mismatch | Clean contacts; format in the camera. |
| Phone asks to format | Different encryption or format | Back up on the source device; choose portable mode. |
Step-By-Step: Clean, Repair, Then Format
1) Clean Contacts And Reseat
Gently wipe the pads, blow away dust, and reseat the card. Test again.
2) Try Another Reader Or Device
Readers fail often. Borrow one or use a camera in USB reader mode. Swap cables. Avoid hubs.
3) Repair The File System
On Windows, run Error Checking or chkdsk. On macOS, run First Aid. If the tools report bad blocks or unrepairable structures, move to recovery and replacement.
4) Back Up Anything You Can
Copy intact folders first (DCIM, MOVIE, MUSIC). Then try a recovery pass for partial files.
5) Format With The Right Tool
Use the official SD utility on computers when a device won’t format cleanly. Pick quick format for a fast refresh, full format only when you need a media scan. After a clean format, run a short write-read test before returning the card to mission use.
Why Card Formats Matter
FAT32 tops out at 4 GB per file and 32 GB per typical Windows quick format dialog. exFAT removes the single-file limit and ships as the standard on large cards. NTFS works on Windows but causes trouble in cameras and many readers, so skip it for removable media outside of PCs. Matching format to device avoids mount loops and naming oddities.
When To Replace The Card
Flash wears out. If a card starts throwing errors again after a clean format and a good reader, retire it. Keep spares on hand for paid shoots or travel days. Label cards with date of first use so you can rotate before wear shows up in the worst moment.
Prevent Problems Next Time
- Always eject before you pull a card.
- Format in the destination device after copying finished work.
- Avoid mixing one card across many devices that write differently.
- Keep cards dry and capped; wipe pads if you see grime.
Helpful Official References
The SD Association publishes a small desktop formatter that applies the standard for each family. Apple documents the steps for Disk Utility First Aid. Microsoft has a full reference for the chkdsk command. Use these when you need the exact menus and wording.