Quick Answer
There are a few common reasons why an SD card may not be able to be formatted:
- The SD card is corrupted or damaged
- The SD card is write-protected
- There is not enough free space on the computer to complete the format
- The SD card is locked by the device it is inserted in
- There is a problem with the SD card reader or cable
SD Card is Corrupted or Damaged
One of the most common reasons an SD card cannot be formatted is because the card itself is corrupted or damaged in some way. This can happen for a variety of reasons:
- Improperly ejecting the SD card from a device before removing it
- Exposure to heat, moisture, or physical damage
- Power outages or interruptions while writing data to the card
- The age and wear of the SD card over time leading to degraded performance
When an SD card becomes corrupted, it can start to exhibit strange behaviors like not being recognized by devices, files disappearing from the card, or being unable to save new data. The operating system may detect errors on the card and prevent formatting as a protective measure.
Formatting the card overwrites data on the card, which can further damage a corrupted card. To recover corrupted data on the card, special software tools may be required before attempting to reformat again.
If the SD card is physically broken with damaged contacts or internal memory chips, a format will not be able to fix it. A physically damaged card that cannot be formatted will need to be replaced.
SD Card is Write-Protected
Another possibility is that the SD card has been write-protected, which blocks new data from being written to it.
SD cards have a small slider switch on the side that can toggle between a locked or unlocked position. If the lock switch is slid down to the locked position, it will prevent files from being added, deleted, or edited on that card.
Attempting to format a locked SD card will result in an error, since formatting requires writing data to the card. Simply unlocking the write-protect switch should allow the card to be formatted normally again.
The write-protect lock also serves as a safeguard against accidentally deleting or overwriting files on the SD card. When working with card readers or cameras, double check that the lock is in the unlocked position if having issues formatting.
Not Enough Free Space on Computer
The computer that the SD card is connected to requires sufficient free disk space to be able to complete the formatting process. This is because the operating system needs allocated space to temporarily copy technical information and file tables during the format.
If the computer is nearly full on its own internal hard drive, it may not have enough room to fully format the external SD card. This can result in format errors or failures.
To resolve this issue, free up additional storage space on the computer by:
- Deleting unnecessary files and emptying the Recycle Bin
- Uninstalling unused programs
- Moving files to external storage drives
After creating sufficient free space (at least a few GB extra is recommended), try formatting the SD card again.
SD Card Locked by Device
If the SD card is inserted into a device like a camera, phone, or voice recorder, some of these devices may lock or ‘mount’ the card while they are accessing it.
When locked by the device, the card is in use and cannot be accessed externally until the device releases the lock. Attempting to format an SD card that is locked by a device will result in errors.
To release the card lock, the SD card should be safely ejected or unmounted from the original device first before removing it physically. This ensures all data gets flushed from cache and the device properly releases the card.
Once safely ejected or unmounted, the SD card can then be inserted into a card reader or another device and should be able to be formatted.
SD Card Reader/Cable Connection Issue
Finally, there may be a physical connection problem with the SD card reader or cable that links the SD card to the computer.
Some things to check in this situation include:
- Trying different USB ports on the computer in case one is damaged
- Checking that the SD card clicks fully into place in the card reader
- Inspecting the end of the USB cable for bent pins or damage
- Using a different USB cable to connect the card reader
- Trying the SD card in a different brand of card reader or device
If a physical connection issue is found, replace any damaged cables or faulty hardware. USB ports and readers can sometimes become worn out over time with frequent use.
If the SD card cannot be accessed by multiple computers and readers, then the card itself is likely corrupted or damaged instead.
How to Fix Unformattable SD Cards
If your SD card cannot be formatted, try the following solutions:
Check and Unlock Write Protection
Make sure the slider on the side of the SD card is in the unlocked position so data can be written to it.
Eject and Unmount Card
If inserted in a device, use the safe remove feature to eject the SD card before physically removing it. This releases any lock the device has on it.
Use Disk Utility
On Macs, use Disk Utility to erase the SD card. On Windows, access disk management and recreate the volume to wipe the card.
Delete Partition
Use disk management on Windows or Terminal on Mac to enter diskpart, then use commands like select disk, clean, and create partition to recreate the layout.
Low-Level Format
Use third-party tools like SD Memory Card Formatter or HDD Low Level Format Tool to do a complete low-level format of the card.
Last Resort: Replace Card
If nothing else works, the SD card may be permanently damaged and need replacement. Copy any recoverable data off the damaged card beforehand using data recovery tools if possible.
Tips to Avoid Unformattable SD Card Issues
Here are some tips to prevent your SD card from becoming corrupted or damaged in the first place:
- Safely eject the SD card before removing it from devices
- Store cards properly in a protective case when not in use
- Avoid exposing cards to water, heat, or dropping
- Handle the card gently by the edges to avoid bending
- Don’t store cards near magnetic fields or static electricity
- Use high quality brand name SD cards
- Back up your files regularly in case a card gets damaged
Following best practices for handling and storing SD cards will help maximize their lifespan and avoid format issues down the road.
FAQs on Formatting an SD Card
Can I recover files after formatting an SD card?
Once an SD card is formatted, any existing files and data on the card are erased and no longer accessible. However, with the right data recovery software, it is sometimes possible to recover lost files after a format, as long as they have not been overwritten by new data yet.
Is formatting an SD card necessary?
Formatting an SD card is recommended for cleaning up errors, preparing the card for a new device, permanently deleting data, and restoring full performance. However, it is not absolutely necessary in all cases. Simply deleting files or using disk cleanup utilities can work too.
How long does formatting an SD card take?
The time to format an SD card depends on the card capacity and computer speed, but generally takes just a few minutes for most consumer cards up to 32GB. Larger cards or a full low-level format can take much longer, up to an hour for terabyte sized cards.
Can I stop formatting an SD card midway?
It is not advisable to stop the formatting process midway, as this can further corrupt the card. The best approach is to wait for the format to fully complete before removing the card. If needed, use Task Manager on Windows or Force Quit on Mac to cancel a stalled format process.
Should I format new SD cards before first use?
Brand new SD cards can optionally be formatted before first use, but it is not strictly necessary nowadays. Cards come pre-formatted by manufacturers. Quick formatting can still help prepare cards for the device expected to use them.
Conclusion
SD cards failing to format properly is a common issue that can occur due to physical damage, corruption, write protection, insufficient computer disk space, or connection problems. Following troubleshooting steps like using disk utility tools, changing card readers, unlocking the card’s write protection, or low-level formatting may help get an unformattable card working again. In severe cases where the card is beyond repair, replacement will be necessary. Taking general precautions in how SD cards are handled and stored can help maximize their lifespan and avoid format issues.