How do I know if my micro SD card is working?

Micro SD cards have become a popular way to expand the storage capacity of devices like smartphones, tablets, and other electronics. But sometimes it can be unclear if the micro SD card is actually working properly. Here are some tips for how to check if your micro SD card is functioning correctly.

Try accessing files on the SD card

The most basic way to check if your micro SD card is working properly is to simply try opening files that are saved on the card. Insert the micro SD card into your device, then open the file manager or gallery app and browse to the SD card storage. Try opening photos, videos or other files that you have saved on the card. If you are able to open the files without issue, then your SD card is likely working fine.

Things to look out for when accessing files:

  • Errors opening files – If you get error messages when trying to open files on the SD card, that indicates a problem with the card.
  • Corrupted files – If files appear corrupted or can’t be opened, the card may be damaged.
  • Missing files – If files you know you saved previously aren’t showing up, the SD card may not be readable.

Check if the SD card is detected by your device

In order for your device to be able to access files on the micro SD card, it will need to properly detect and mount the card. Here’s how to check if your device recognizes the SD card:

On a smartphone or tablet:

  • Go to Settings > Storage – There should be an entry for the SD card listing the total and available storage space.
  • Reinsert the SD card – Remove and reinsert the SD card then check Storage again. The entry for the SD card should disappear then reappear if detectable.

On a computer:

  • Open File Explorer – The SD card should be listed as a drive letter if properly detected.
  • Open Disk Management – The SD card should be listed as a disk drive here.

If your device is not detecting the micro SD card, there is likely an issue with either the card or the device’s card reader. Try the card in a different device to narrow down the cause of the issue.

Check the SD card’s filesystem

Another way to validate your SD card is working properly is to check its filesystem for errors. The filesystem is the structured way data is stored on the card. Here’s how to analyze the filesystem on different devices:

On Windows:

  • Open Command Prompt as Administrator
  • Run “chkdsk x: /f” where x is the drive letter of your SD card
  • Let the scan run – chkdsk will fix any filesystem errors it finds

On Mac:

  • Insert SD card into a card reader if necessary
  • Open Terminal
  • Run “diskutil verifyVolume /Volumes/NAME” where NAME is the name of your SD card
  • Let the verification run to completion

On Linux:

  • Open a Terminal window
  • Run “fsck -f /dev/mmcblk0p1” or similar where /dev/mmcblk0p1 is the SD card mount point
  • Allow fsck to check and repair filesystem errors

If errors are reported when checking the filesystem, you may need to reformat the SD card to repair corruption issues.

Look for physical damage on the card

In some cases, physical damage to the SD card could be causing issues. Carefully inspect the card for any signs of:

  • Chips/cracks in the plastic casing
  • Bent or misaligned contacts
  • Corrosion on the metal contacts
  • Burn or heat damage

Any physical damage could interfere with the proper operation of the card and may require replacing it entirely.

Test the card’s read/write speed

To further validate the performance of your micro SD card, you can test its read and write speeds. Low read/write speeds can indicate a counterfeit or faulty card.

On Windows:

  • Use a benchmark tool like CrystalDiskMark to test read/write speeds
  • Compare results against your SD card’s advertised speeds

On Mac:

  • Use Finder to copy a large file (1GB+) on and off the SD card
  • Time the transfer speed with a stopwatch
  • Divide the file size by transfer time to get MB/s

On Linux:

  • Use a tool like dd or rsync to test read/write speeds
  • Time transfers with a command like ‘time dd if=/dev/sdb of=/dev/null bs=8M count=1024’
  • Check output for transfer rate statistics

If your card’s speeds are much lower than its rating, it may be a counterfeit or be failing.

Reformat the SD card

If you still have issues after trying the steps above, reformatting the SD card may help get it back into a usable state. Reformatting erases all data on the card and recreates the filesystem.

On Windows:

  • Use Windows Explorer to right-click on the SD card and select Format
  • Choose FAT32 or exFAT filesystem
  • Start the formatting process

On Mac:

  • Open Disk Utility
  • Select the SD card volume
  • Click Erase and choose a name, format, and scheme
  • Erase the volume to reformat the card

On Linux:

  • Use GParted to select the SD card drive
  • Choose Device > Create Partition Table
  • Create a new partition with the desired filesystem
  • Click Apply to reformat the card

Reformatting will erase all data but may resolve performance issues if the card’s filesystem was corrupted.

Replace the SD card

If you continue having issues after trying all other steps, the micro SD card may need to be replaced. Some signs it’s time to replace an SD card include:

  • Card is several years old
  • Errors persist after reformatting
  • Card has been damaged or exposed to extreme heat/moisture
  • Card performs far below advertised read/write speeds
  • Card has very low capacity compared to current offerings

Purchasing a new micro SD card from a reputable retailer should resolve any ongoing issues you may be having.


Here are some key points to keep in mind when troubleshooting micro SD card issues:

  • Try accessing files on the card to check basic functionality
  • Confirm your device detects the card in storage settings
  • Check for filesystem errors using chkdsk, fsck, or similar utilities
  • Inspect card for any physical damage
  • Use tools to test read and write transfer speeds
  • Reformat the card if other issues are ruled out
  • Replace the card if problems persist after troubleshooting

Following these steps should help identify if your micro SD card is working correctly or determine if a replacement is needed. Properly functioning SD cards are crucial for expanding storage space on smartphones, cameras, and other devices.