Why is my SD card suddenly not reading?

Having an SD card stop working unexpectedly can be incredibly frustrating. One minute your device is reading the card just fine, and the next minute it’s like the card doesn’t even exist. There are several potential causes for an SD card suddenly becoming unreadable. In this article, we’ll walk through the most common reasons your SD card may have stopped working and offer troubleshooting tips to get it up and running again.

Corrupted File System

One of the most common reasons an SD card will suddenly stop working is because its file system has become corrupted. The file system is essentially the card’s “table of contents” – it’s what allows the operating system to make sense of all the data on the card. If this gets damaged or corrupted, the device is unable to access the files.

A corrupted file system can occur for a number of reasons:

  • Improperly ejecting/removing the SD card from a device
  • A sudden power outage while writing data to the card
  • Too many read/write cycles over the life of the card causing logical errors
  • Malware or other files saving improperly to the card
  • Physical damage to the card itself

If you suspect your SD card file system has become corrupted, the first thing to try is simply reformatting the card. This essentially creates a new blank file system, wiping out the old corrupted one in the process. Follow these steps:

  1. Insert the SD card into your computer if it isn’t already.
  2. Open Disk Utility on Mac or This PC/File Explorer on Windows.
  3. Select the SD card volume.
  4. Click “Format” to erase and reformat the volume.

This should create a fresh, empty file system on your SD card. You can then try adding files again to see if it is now functioning normally. Any data that was on the card prior to formatting will be erased, so be sure you don’t need anything on the card before reformatting.

If reformatting doesn’t work, it’s likely there is a bad sector or physical problem with the card that requires other solutions covered below.

Bad Sectors

While less common than file system issues, bad sectors can also cause an SD card to suddenly stop reading properly. Bad sectors are small portions of the card that have become physically damaged and can no longer reliably save data. This damage often occurs over time as the card is used over and over.

Some signs your SD card may have bad sectors:

  • Errors when copying files to or from the card
  • Files disappearing from the card
  • Frequent crashing/freezing when using the card
  • The card becoming read-only

Trying to reformat a card with bad sectors will not fix the issue since the physical damage remains. However, you may be able to repair some bad sectors using the chkdsk tool on Windows or Disk Utility First Aid on Mac.

To run chkdsk on Windows:

  1. Insert SD card into your computer.
  2. Open the Start menu and search for “cmd” to open the Command Prompt.
  3. Type “chkdsk x: /f” where x is the letter of your SD card drive.
  4. Allow chkdsk to run – this can take some time if there are a lot of errors.

On Mac using Disk Utility:

  1. Open Disk Utility.
  2. Select your SD card volume.
  3. Click First Aid in the toolbar.
  4. Allow the repair process to complete.

This will go through and scan your SD card for bad sectors, attempting to repair any issues it finds. If chkdsk is successful at repairing the damage, your SD card should start working again properly. If the card still isn’t working right after chkdsk, then there is likely irreparable physical damage.

Physical Damage

As mentioned above, one of the most common reasons an SD card might stop functioning is due to physical damage to the card itself. This can include:

  • Dust, dirt, or debris inside the card slot
  • Bent or broken connector pins
  • Visible scratches/dents/markings on card surface
  • Damage due to shock, heat, magnets, static, etc

Unfortunately once an SD card has become physically damaged, there is likely no way to repair it. However, there are some troubleshooting steps you can try on your own before fully giving up hope:

  • Try inserting the card into a different device like a phone, camera, or USB reader.
  • Gently clean the contact points on the card with isopropyl alcohol.
  • Check the SD slot for debris and clean if needed.
  • Carefully straighten any bent connector pins if possible.
  • Allow card to sit untouched overnight which can sometimes resolve issues.

If after trying the above the card still won’t read, then it will need to be replaced. Thankfully SD cards have become very affordable, with many options available for under $20 online or at your local electronics store.

When buying a new card, look for name brands like SanDisk or Samsung rather than generic no-name brands. Also be sure to get the right type – SD cards come in sizes from 4GB to 1TB and speeds from U1 to U3/V30. Check your device’s manual if you’re unsure what card capacities and speeds are compatible.

Bad SD Card Reader/Port

While not as likely as a problem with the SD card itself, occasionally the card reader or SD card port is to blame for connectivity issues. This can happen due to normal wear and tear over time. Dust build up or corrosion inside the port can prevent the pins from making solid contact with your card.

You can test whether the problem is with your SD card or the device’s reader/port by trying the following:

  • Try your SD card in a different device like a computer, phone, camera etc.
  • Try a different known working SD card in your device’s port.

If your card works fine in other devices, but a different card has problems in your device, then the issue is with your device. If your device reads other cards with no issue, then your original card is likely faulty.

For cleaning a dirty SD card port, use a can of compressed air to blow out any debris. You can also use a toothpick or soft brush dampened with isopropyl alcohol to gently clean the port. Avoid using anything metal or abrasive that could scratch the pins.

If cleaning doesn’t resolve port connectivity problems, you may need to have your device serviced by a repair shop. They can diagnose issues with the reader hardware itself and potentially replace the component if needed.

Incompatible File System

One other less common possibility – your SD card may suddenly stop working if it’s formatted with a file system that your device doesn’t support.

For example, you may have formatted the card on a Linux system as EXT4, but then try to use it on a Windows PC that only supports FAT32/exFAT formats. Or formatted it for use in a digital camera expecting a proprietary file system.

Reformatting the SD card to a compatible file system can resolve this issue. Use the manufacturer’s recommendations to determine the proper format type for your device, then redo the card in that format. This will wipe all current data, so be sure to offload anything important first.

Here are some of the most common file system formats used on SD cards and where they are supported:

File System Compatible Devices
FAT32 Windows, Mac, Linux, Game Consoles, Cameras
exFAT Windows, Mac, Game Consoles, Cameras
NTFS Windows
EXT4 Linux
HFS+ Mac

So for widest compatibility, FAT32 or exFAT are generally the best options for SD cards unless you specifically need it for one type of device only.

Permission Issues

Occasionally your SD card may suddenly go read-only or be inaccessible due to permission problems between the operating system and the card’s data. This is especially common when using SD cards between different devices and OSes like Windows, Mac, mobile, and cameras.

A permission conflict can manifest in different ways, such as:

  • Not being able to modify or delete files/folders on the card
  • Constant read-only errors when trying to save to the card
  • Some files being inaccessible or looking like corrupted data

To fix permission issues on an SD card, you will again need to reformat it. But this time, be sure to reformat using the OS you primarily intend to use the card on:

  • For Windows – Reformat as NTFS or FAT32 in File Explorer
  • For Mac – Reformat as exFAT or FAT32 in Disk Utility
  • For Linux – Reformat as EXT4 in Gparted

Alternatively, use the SD Association’s official SD Formatter tool available for Windows and Mac. This will format your card to be compatible with all types of devices again.

Reformatting sets the permissions back to default for that OS. Just be aware you may run into permission issues again if switching frequently between devices and operating systems.

Card Locked

Some SD cards and devices include a physical write-protect “lock” switch on the card itself. This switch lets you toggle the card between a locked “read-only” state and unlocked writeable state.

If your card suddenly appears read-only, isn’t saving files, or gives errors when trying to modify data, check to see if the lock switch has been toggled to the lock position. Just slide the switch back to unlock and you should regain write access.

Note that on microSD cards and some smaller form factors, the lock switch consists of a single small tab on one edge rather than a labeled slider switch. Check your card closely for a movable plastic tab.

If there is no physical lock switch on your SD card, then any read-only issues are caused by something else. Software problems are more likely the culprit than a missing hardware switch.

Outdated SD Drivers

For SD cards not being read properly on Windows machines, occasionally the issue is outdated device drivers rather than the card itself. The SD card reader in your computer relies on drivers provided by Windows to operate correctly.

If these drivers have bugs, are outdated, or are misconfigured, your SD card may not show up or encounter connectivity issues even if the card is perfectly healthy.

Fixing drive issues on Windows involves first identifying the specific SD card reader hardware in your computer, determining the current driver and version, and then updating or reinstalling the driver:

  1. Open Device Manager > View USB controllers.
  2. Locate the USB device for your SD card reader.
  3. Right click Properties > Driver tab to see driver provider and version.
  4. Visit the provider’s website to download updated driver software.
  5. Uninstall the old driver and restart your computer.
  6. Install the updated driver and restart again.

This will refresh the driver software powering your SD card reader. If it was a driver problem, your card should now be detected properly again in Windows Explorer.

You can also use the Device Manager rollback option to revert your driver to a previous working version if updating drivers doesn’t resolve the problem.

Faulty SD Card Slot

At times, the SD card slot itself might be damaged, resulting in connectivity problems including being unable to read cards. This could happen due to:

  • Loose solder joints inside the slot
  • Scratched or bent contact pins
  • Dislodged components
  • Liquid spills or debris inside the slot

Issues with the physical SD card reader can be tricky to diagnose and repair as a non-technical user. However, you can try these DIY troubleshooting steps before paying for professional repair:

  • Visually inspect card slot pins for any obvious damage
  • Use compressed air to clean out any debris inside the slot
  • Check the SD card sits flush when inserted
  • Try gently reseating the SD card reader cable connections

If you’re comfortable disassembling the device, you can open it up to better inspect the SD card reader and connections. But be extremely careful not to damage any internal components if attempting this.

For laptops, the SD slot is often part of a larger removable card reader module. You may be able to find a replacement part online to swap in yourself, as long as you match the exact module model.

For problems inside smartphones and other small electronics, repair will likely require professional microsoldering equipment to reflow joints and properly replace any components. Seek out a reputable electronics repair shop for assistance.

Corrupt SD Card Data

Instead of a hardware issue with the SD card itself, sometimes the existing data on the card becomes corrupt or damaged. This can happen for reasons like:

  • Removal during a write/save operation
  • Power failure or crash during read/write
  • Faulty readers or writers
  • Bugs in data saving software
  • Viruses or other malware

Corrupted data essentially makes files on the card unreadable by the system. The card may show up and be accessed, but yield errors when trying to open files or copy data on/off it.

Formatting the SD card is typically the solution here as well. This will wipe all current data, letting you start fresh and write new intact files to the card.

Some signs of data corruption include:

  • Frequent read/write errors and crashes
  • Files missing chunks or showing up blank
  • Data being scrambled or nonsensical
  • Unusable files despite card appearing normal

Before formatting, you may want to attempt data recovery if the files are important. Use recovery software like Recuva or EaseUS Data Recovery Wizard to scan the card and rescue any retrievable data.

Going forward, make sure to properly eject the card before removal and avoid corruption by:

  • Using brand name high quality SD cards
  • Following proper read/write procedures
  • Using anti-malware software
  • Backing up important files off the card


SD cards not being detected or read can lead to a lot of frustration. But in most cases, the issues can be resolved with basic troubleshooting steps like reformatting, cleaning the hardware connections, or inspecting the card reader. Contact a specialist if you exhaust all DIY solutions without the SD card working properly again.

To avoid issues in the future, purchase reputable SD cards, follow proper care guidelines, and watch for early signs of problems like read errors or slow performance. Managing your data backups off the SD card will also prevent file loss if the card becomes damaged or corrupted.