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Everything you need to know about SD cards

There's a wide variety of SD cards available on the market, with the most common being the standard SD card and the microSD card. They're mostly used with digital cameras as well as with a few less common devices, like multimedia players.

But even within the most common SD card formats, there's a lot of variety, and it's important to know about the differences in order to make the best choice when you're buying an SD card.

1. What's the difference between SD, SDHC, SDXC, and SDUC?

People have an increasing need for higher capacity SD cards with higher file-transfer rates. So over the years, there have been a host of new SD versions to help meet these demands. These include SDHC (SD High Capacity), SDXC (SD eXtended Capacity), and SDUC (SD Ultra Capacity). See the table below for full details.

SD card version	SD	SDHC	SDXC	SDUC
Minimum capacity	8 MB	2 GB	32 GB	2 TB
Maximum capacity	2 GB	32 GB	2 TB	128 TB
File system	FAT 12/16	FAT 32	exFAT	exFAT
Year of release	1999	2006	2009	2018
SD specification	SD 1.0	SD 2.0	SD 3.0	SD 7.0

2. What's the difference between UHS-I, UHS-II, UHS-III, and SD Express?

"UHS" is the abbreviation of "Ultra-High Speed". UHS memory cards generally have faster reading and writing speeds. This standard is formulated by the "SD Card Association", a non-profit organization, and there are several versions:

UHS-I (the first generation of ultra-high speed) was released in 2010, and the theoretical transmission speed can reach a maximum of 104 MB/s. It's suitable for daily use, such as taking photos and recording videos.

UHS-II SD cards can reach 312 MB/s which is suitable for taking high-definition video and high-definition pictures in 4K.

The UHS-III specification was released in early 2017, doubling the previous UHS-II rate and achieving unprecedented transfer speeds of up to 624 MB/s. It's suitable for devices that need really fast data transfer, for example, professional cameras used to record 8K, 4K, and 360-degree video.

SD Express offers the fastest data transfer rates of up to 3940 MB/s using the PCIe Gen.4 interface and NVMe application protocol. It supports dual-channel reading, and the interface speed is close to 4 GB/s. Unfortunately, there aren't any devices that have adopted this standard yet, but in the future, it should mean we can enjoy much faster data transfer speeds.

Bus Interface	Card Type	Bus Mark	Bus Speed	Spec Version
Default Speed	SD, SDHC, SDXC and SDUC	—	12.5 MB/s	1.01
High-Speed	SD, SDHC, SDXC and SDUC	—	25 MB/s	1.1
UHS-I	SDHC, SDXC and SDUC		50 MB/s (SDR50, DDR50) 104 MB/s (SDR104)	3.01
UHS-II	SDHC, SDXC and SDUC		156 MB/s Full-Duplex 312 MB/s Half Duplex	4
UHS-III	SDHC, SDXC and SDUC		312 MB/s Full-Duplex 624 MB/s Full-Duplex	6
SD Express	SDHC, SDXC and SDUC		985 MB/s PCIe Gen.3 × 1Lane	7
			1970 MB/s PCIe Gen.4 × 1 Lane PCIe Gen.3 × 2 Lane	8
			3940 MB/sPCIe Gen.4 × 2 Lane	8

3. How to choose the right card reader for you？

It's important to make sure that the card reader you're buying is compatible with your memory cards. In addition, you should choose your memory card based on your personal needs. If it's for daily use, a microSD card or SD card with UHS-I will get the job done. If you need something with higher performance, then a UHS-II SD card would be a better choice.

Another thing to consider is that since 2016, Apple has switched to USB-C ports on its laptops, and has stopped including a card reader as standard. This means that MacBook users will need to buy an adapter or a USB-C to SD card reader.

If you have any further questions, please contact us for assistance.