Will an SDXC card work in SD slot?

The Difference Between SD, SDHC and SDXC Cards

The original SD card stands for Secure Digital and was introduced in 1999 with capacities up to 2GB. SDHC, which stands for Secure Digital High Capacity, was introduced in 2006 and supports capacities between 4GB and 32GB. Finally, SDXC stands for Secure Digital Extended Capacity and was launched in 2009. SDXC cards can store up to 2TB of data (AZ Central).

In terms of speed, original SD cards have a maximum transfer speed of 25MB/s. SDHC cards can go up to 104MB/s. The fastest SDXC cards now exceed 300MB/s for reading and 260MB/s for writing (Integral Memory). So in summary, the main differences are SDXC offers vastly greater storage capacity while also providing faster transfer speeds.

Backwards Compatibility of SD Cards

SDXC cards are physically backwards compatible with SDHC and SD slots despite having greater storage capacities. This means you can insert an SDXC card into an SDHC or SD host device slot and it will fit inside the slot without issues [1]. The key difference between SD, SDHC, and SDXC cards is primarily in the maximum storage capacity – SD supports up to 2GB, SDHC supports up to 32GB, and SDXC supports up to 2TB. However, the physical dimensions of all three card types are exactly the same.

So in terms of physical backwards compatibility, you can use a higher capacity SDXC card in an older SD or SDHC host device slot. The SDXC card will fit inside the slot without any issues since the physical shape and dimensions are the same across all three card types.

The Importance of ExFAT File System

SDXC cards with a capacity larger than 32GB use the exFAT file system while SD and SDHC cards use the FAT32 file system. exFAT was introduced in 2006 and is optimized for flash memory like SD cards, allowing support for large file sizes beyond 4GB.[1]

The advantage of exFAT is that it can handle the very large capacity SDXC cards. However, the downside is that older devices manufactured before exFAT was introduced may be incompatible. This means if you insert an SDXC card formatted with exFAT into an older device, it may not be readable.[2]

Therefore, it’s important to check if your device supports exFAT before using an SDXC card. Some older devices are limited to the FAT32 file system and cannot read SDXC cards out of the box unless they are reformatted, losing capacity over 32GB.

SD Slot Standards and Speeds

SD slots support different standards that determine the maximum speeds the card can reach. The main standards are:

  • SD (up to 12.5 MB/s)
  • SDHC (up to 104 MB/s)
  • SDXC (up to 104 MB/s)
  • UHS-I (up to 104 MB/s)
  • UHS-II (up to 312 MB/s)
  • UHS-III (up to 624 MB/s)

Within these standards there are also speed classes that indicate the minimum guaranteed speeds. Speed classes like Class 2, Class 4, Class 6, Class 10 and U1, U3 indicate the minimum write speeds in MB/s. Faster cards have higher speed class ratings.

Newer UHS standards like UHS-II and UHS-III allow for much faster speeds by using additional physical pins and interfaces. Most current devices still use UHS-I or below.

According to the SD Association, “New SDXC host devices are required to accept SDSC and SDHC cards in accordance with earlier versions of the specification.” (https://www.sdcard.org/developers/sd-standard-overview/)

Real-World Performance in Older Devices

While SDXC cards are backwards compatible, some users have reported slower speeds when using them in older devices with SD slots. According to a Reddit thread, using a cheap or old SD card can negatively impact phone performance, but decent Class 10 or UHS cards generally will not[1]. In a video by Tom’s Tech Time, several microSD cards were tested in devices advertising different speeds. The results showed some cards performed significantly slower than their rated speeds, so actual performance depends on the specific card and device[2].

In summary, while SDXC cards are backwards compatible, you may experience slower speeds in older devices. However, with a decent quality card you can expect reasonable performance.

Reasons SDXC May Not Work

There are a few key technical reasons why an SDXC card may not work in an older device designed for SD or SDHC cards:

SDXC cards use the exFAT file system, while SD and SDHC cards use FAT32. Older devices may lack support for exFAT, which was introduced in 2006. Without exFAT support, the device won’t be able to read the SDXC card (Sandisk Forums).

SDXC cards have higher maximum capacities, up to 2 TB. Older devices may have limits coded in that don’t recognize cards above 32GB (the max capacity for SDHC). Trying to use a high capacity SDXC card may result in errors.

SDXC cards are designed for faster interface speeds. Using an SDXC card in an older SD slot limited to slower speeds may result in poor performance or instability (Raspberry Pi Forums).

Overall, SDXC requires both software exFAT support and hardware that can handle the higher capacities and speeds. Lacking either can cause problems.

How to Check Device Compatibility

Before purchasing an SDXC card, it’s important to verify that your device actually supports the format. Here are some tips for checking compatibility:

For smartphones and tablets, check the manufacturer’s website or user manual. Many list the maximum supported SD card capacity, and capacities over 32GB imply SDXC support.

You can also look for the SDXC logo on the device or its packaging. The SDXC logo indicates the device meets the standards required for SDXC.

On Windows PCs, open the Device Manager and view the properties for the SD card reader. Details on the driver and standards supported are typically listed.

On Mac computers, check System Information for the model/chipset of the SD card reader. Research the specs online or contact the manufacturer.

For dedicated cameras, look in the user manual or contact customer support to verify SDXC support. High-end DSLRs commonly include it.

As a rule of thumb, SDXC support started emerging around 2010. Older devices predating SDXC are unlikely to be compatible.

Testing the device with a low-capacity SDXC card is also an option. If it’s recognized and functions normally, full compatibility is confirmed.

Solutions and Recommendations

If your SDXC card isn’t working properly in an older device, there are some things you can try:

  • Reformat the SDXC card – Use your computer to reformat the card to FAT32 or exFAT. This will erase all data but may allow the card to work in older devices.
  • Update device firmware – Check with the device manufacturer for any firmware updates that may add SDXC support.
  • Use a different SDXC card – Try a different brand or speed of SDXC card, as some may be more compatible than others.
  • Use an SDXC to SDHC adapter – This allows you to physically insert an SDHC card, which is compatible with older devices.
  • Buy an SDHC card instead – SDHC cards come in capacities up to 32GB and are compatible with older hosts. They are more widely supported than SDXC.
  • Check host device documentation – The user manual or specs should indicate if SDXC is supported. If not, an SDHC card is the safer option.

In most cases, switching to an SDHC card or using a physical SDXC to SDHC adapter will allow the card to work properly in older devices. Reformatting or trying a different SDXC may also do the trick. If SDXC is definitely not supported, then an SDHC card up to 32GB is recommended.

The Bottom Line

In summary, SDXC cards will generally work in older SD card slots, thanks to backwards compatibility. However, there are some caveats:

  • The device needs to support the exFAT file system used by SDXC cards.
  • Older devices may have speed limitations that hinder SDXC performance.
  • Some very old card readers and devices simply don’t recognize SDXC capacities.

To ensure compatibility, check your device’s manual and specifications. If not, try the SDXC card and test it—it will likely work fine in most cases. But be prepared for the possibility of speed issues or lack of recognition on outdated hardware.

So in summary—yes, SDXC cards will technically function in standard SD slots. But very old devices may have issues due to speed or capacity limitations.


Here are some sources you can reference for further reading on SDXC cards and backwards compatibility:

You can find detailed technical specifications for SD slots and cards on the SD Association website.