What does SDXC Stand for on My 256GB SD Card?

If you’ve recently purchased an SD card, you might notice some additional letters on the side. Sometimes, the card might read ‘SDHC.’ Other times it might be ‘SDXC.’ Any 256GB card is SDXC, for instance. What do these letters mean and how are they different from plain old SD cards.

While those letters might look technical and confusing, their meaning is extremely straightforward. SDHC stands for ‘Secure Digital High Capacity.’ SDXC stands for ‘Secure Digital eXtended Capacity.’ If you buy an SDXC 256GB card, you are buying a card that falls into the ‘extended capacity’ range (32GB to 2TB), hence the SDXC letters. Any cards between 4 and 32GB of capacity are ‘high capacity’ cards, hence SDHC. Anything under 4GB is a standard SD card.

Capacity is the only difference from SD to SDHC to SDXC. These letters have no other implications. They do not, for instance, affect the write/transfer speed of the card. Write speed is instead determined based on ‘Class.’ You will notice a number in a circle on your card, with the possible numbers being 2, 4, 6, 8 and 10. Each number corresponds to the minimum number of megabytes the card can write transfer per second on a sustained basis. In other words, the higher the class number, the faster the card. The UHS speed class is displayed with numbers 1 or 3 placed inside the letter U which show the minimum sustained write speed 1 being 10MB/s and 3 being 30MB/s. The new Video Speed Class displayed as V6, V10, V30, V60 or V90 for constant data recording performance. The U3 and V30 is required for 4K video.

As you shop for 256GB SDXC cards (or any other SD card, for that matter) take note of the class number. If you plan on using your card for intense data transfer purposes—such as transferring a lot of video from an action camera to your computer—you will want to have a faster card.

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