There are a few common reasons why your micro SD card may not be reading properly when you insert it into your device:
The card is corrupted
One of the most common issues is a corrupted memory card. This can happen if the card was not ejected properly from a device before being removed, if there was a power outage or device crash while the card was in use, or if the card has become worn out from excessive use and reuse. Corrupted cards often show errors or fail to show any files at all when inserted into a device.
The card is formatted incorrectly
Another possibility is that the card is formatted with the wrong file system for your device. Most consumer devices require micro SD cards to be formatted as FAT32 or exFAT. If your card is formatted as a different file system like NTFS or HFS+ then your device may not recognize it.
There are hardware issues with the card
Faulty hardware can also prevent a micro SD card from being read. Problems like bent or broken pins on the contact area, internal errors in the memory modules, or issues with the controller chip can all lead to access issues. In most cases there is no way to repair hardware problems on micro SD cards, so cards with physical damage will need to be replaced.
The card is not inserted correctly
It may sound obvious, but double check that your micro SD card is oriented correctly and fully inserted into the slot. Cards need to be put in with the contact pins facing down and gently pushed in all the way until the locking mechanism clicks. If not fully inserted, the device will not make a proper connection and will not detect the card.
The card lock switch is enabled
Many micro SD cards have a tiny switch on the side that can toggle write protection on and off. If this switch is slid to the lock position, it will prevent devices from writing data to the card. Make sure the lock switch is disabled in the unlocked position so that the card can be accessed fully.
The device needs to be restarted
In some instances, glitches with the operating system can prevent memory cards from being detected even when inserted properly. Rebooting the device fully can help reset things and allow the SD card to be recognized correctly after restarting.
The card reader or slot is damaged
The issue preventing your micro SD card from reading may not be with the card itself, but with the hardware used to access it. Damaged or malfunctioning card readers and device slots can interfere with the system detecting memory cards. Trying your card in a different device or reader can help determine if the issue is with the physical access components.
The card is too large for the device
Most consumer devices have limits on the maximum capacity micro SD card they can support. This limit is commonly 32GB, 64GB, or 128GB. Inserting a card that is larger than your device supports will likely result in the card not being detected or not working properly. Refer to your device specifications to determine the maximum SD card size.
The drive letter is not assigned correctly
On Windows computers, SD cards show up as removable drives and are assigned drive letters. If the drive letter was reassigned or is not showing up properly in File Explorer, it may appear that the SD card is not being read. Going into Disk Management and assigning a drive letter can ensure the card shows up correctly.
There are issues with the SD card slot
For built-in card readers in laptops and devices, issues with the SD slot itself could prevent proper detection of cards. This could include dust or debris in the slot, bent pins, or connectivity issues with the slot. Trying the same card in an external USB reader can help isolate issues to the device’s built-in card reader.
The card has low-level formatting issues
On very rare occasions, brand new SD cards may have formatting issues at the disk level that prevent proper initialization and partitioning. Low-level formatting tools like sdcard.org’s SD Formatter can fix these types of deep formatting issues and allow the card to be detected and used properly.
Troubleshooting steps
If your micro SD card is not reading, here are some steps you can take to troubleshoot:
- Check that the card is inserted fully and oriented correctly.
- Inspect the card for any physical damage or broken pieces.
- Try the card in a different device/computer if possible.
- Try a different card in your device to test if the issue is with the device card reader.
- Check if the card lock switch is in the unlocked position.
- Use SD Card Formatter to reformat your card.
- Try reassigning the drive letter in Disk Management on Windows.
- Clean the SD card slot gently with compressed air.
How to fix a corrupted micro SD card
If you determine the issue is a corrupted memory card, here are some steps to try and fix it:
- Connect the card to a computer and run a disk check – on Windows use CHKDSK, on Mac use Disk Utility First Aid.
- Use SD Card Formatter to fully reformat the card. This will erase all data but can fix software corruption issues.
- Try data recovery software to rescue any important files before reformatting.
- If the card has physical damage it likely will need to be replaced.
How to format a micro SD card
Formatting a micro SD card resets it to factory settings and erases all data on the card. Follow these steps:
- On Windows, insert the SD card and open File Explorer. Right click on the card drive and select Format.
- Choose FAT32 or exFAT file system. FAT32 supports up to 32GB cards, exFAT supports larger capacities.
- Adjust any other settings if desired and click Start to begin formatting.
- On Mac, open Finder and click the SD card icon. Click Erase in the toolbar.
- Enter a name, select a format, and click Erase to format the drive.
- You can also use SD Card Formatter for low level formatting on any operating system.
Choosing the right size micro SD card
When buying a new micro SD card, it’s important to choose one that is compatible with your device:
- Check your device’s maximum supported card size – common sizes are 32GB, 64GB, 128GB, 256GB.
- Aim for a higher speed card if your device supports it – minimum of Class 10, UHS-I better for HD video.
- Choose a reputable brand for reliability – Samsung, SanDisk, Kingston, etc.
- Compare prices online to find a good deal.
- Consider how much storage you need for apps, photos, videos, music.
SD card storage capacities
Micro SD cards are available in these common storage sizes:
| Storage | Use Cases |
|---|---|
| 16GB | Basic usage for apps and photos |
| 32GB | Moderate usage for HD photos/videos |
| 64GB | High resolution photos and video storage |
| 128GB | Advanced 4K video, gaming, and multimedia |
| 256GB | Heavy duty high resolution footage and large files |
| 512GB | Extremely large capacity for max storage needs |
SD card speed classes
Micro SD cards are given speed ratings known as classes:
| Class | Minimum Speed | Use Case |
|---|---|---|
| Class 2 | 2MB/s | Basic phone usage |
| Class 4 | 4MB/s | Basic digital cameras |
| Class 10 | 10MB/s | Full HD video recording |
| UHS-I U1 | 10MB/s | 4K video, burst mode photos |
| UHS-I U3 | 30MB/s | Advanced 4K and 8K video |
| UHS-II | 156MB/s+ | Professional high bitrate video |
SD card file systems
Micro SD cards can be formatted with these filesystems:
- FAT32 – Compatible with all devices but max 4GB file sizes.
- exFAT – Allows large capacity cards and files over 4GB.
- NTFS – Optimized for Windows, but not compatible with all devices.
- EXT4 – Used primarily on Linux, limited device compatibility.
- HFS+ – Used mainly on Macs, does not work with most other systems.
For widest compatibility, FAT32 or exFAT are recommended for SD cards unless you specifically need NTFS, EXT4, or HFS+ for a particular device.
Is my micro SD card fake?
Unfortunately, counterfeit micro SD cards are common online and even in some retail stores. Here are signs you may have a fake or improperly manufactured card:
- Price is dramatically lower than major brands
- Unknown or non-existent brand name
- SD card logo is missing or looks incorrect
- Wrong labeled capacity that is larger than expected
- Poor performance that does not match claimed specs
- SD card tester shows high numbers of read/write errors
- Card has very low capacity when first formatted
- Files become corrupted or disappear unexpectedly
Reputable vendors like Amazon, Best Buy, microcenter, and Walmart are safer places to buy real SD cards. But fakes can still end up in their supply chain in some cases.
Conclusion
While micro SD card issues like corruption, fake cards, and incompatible formats can be frustrating, taking the time to troubleshoot and using the right tools can typically get your card back up and running properly. Follow the tips outlined to diagnose what is preventing your card from reading and how to fix various problems that can occur with micro SD cards.
