SD card slot on Apple’s new MacBook Pro supports UHS-II speeds up to 312 MB/s

Apple’s redesigned MacBook Pro notebooks appease photographers, video editors and other creative professionals by bringing back a handy SD card slot along with other I/O ports. Apple has confirmed that the SD card slot in the new MacBook Pro is compatible with the UHS-II protocol though it doesn’t support the fastest UHS-III standard.


  • MacBook Pro’s SDXC card slot is compatible with the UHS-II standard
  • UHS-II supports read and write speeds of up to 312MB/s
  • Creative pros can now quickly transfer files on the go
  • No adapter is needed, just a UHS-II-compatible SD card

Apple's marketing image showing a side view of the 2021 MacBook Pro with the following ports, from left to right: SDXC card, USB-C and HDMI
Left to right: SD card, USB-C and HDMI | Image credit: Apple

How fast is the 2021 MacBook Pro’s SD card slot?

According to the official technical specifications for the 2021 MacBook Pro models that Apple announced during its “Unleashed” product unveiling held on Monday, October 18, 2021, these notebooks are equipped with one SDXC slot for memory cards.

Apple has confirmed to The Verge’s Dan Seifert that both new notebooks — the 14-inch model and its 16-inch counterpart — support the UHS-II protocol, Seifert reported on his Twitter, but not the fastest UHS-III. This means the notebook’s SD card slot offers support for faster memory cards, allowing for quick file transfers between devices.

A traditional SD card (UHS-I) reaches read and write speeds of up to one hundred megabytes per second. With a UHS-II-compliant SD card, however, owners of these new Apple notebooks can enjoy transfer speeds of up to 312 megabytes per second.

For clarity, the 2021 MacBook Pro supports the following SD memory card standards:

  • SD (regular): 12.5 megabytes per second
  • HS (High Speed): 25 megabytes per second
  • UHS-I (Ultra High Speed I): 104 megabytes per second
  • UHS-II (Ultra High Speed II): 312 megabytes per second

The 2021 MacBook Pro does not support these transfer speeds:

  • UHS-III (Ultra High Speed III): 624 megabytes per second
  • HC (SD Express): 985 megabytes per second
  • XC (SD Express): 1.97 gigabytes per second (1970 megabytes per second)
  • UC (SD Express): 3.94 gigabytes per second (3940 megabytes per second)

Does 2021 MacBook Pro support UHS-III?

Again, the new MacBook Pro does not support the latest UHS-III standard which promises transfer speeds in excess of 600 megabytes per second. This isn’t a biggie as UHS-III has yet to become fully adopted by camera makers. Also, you’d be hard-pressed to find UHS-III cards in the wild. Read: Beginner tips for using macOS Finder

Here are maximum storage capacities supported by SD memory cards:

  • SD: 2 gigabytes
  • SDHC: 32 gigabytes
  • SDXC: 2 terabytes
  • SDUC: 128 terabytes

For further information, visit the MacBook Pro webpage on the Apple website.

Why having an SD card slot is important

You can use the SDXC slot on your MacBook Pro to give the notebook additional storage capacity above and beyond its built-in flash storage. And for people who need to transfer large files quickly, an SD card is a far better choice than sitting and waiting until a multi-gigabyte file has finished uploading to Dropbox or a similar cloud storage service.

Wait, I hear you say, I’m not a pro! Relax, SD cards are for everyone who needs to transfer files between devices with ease, not just for video editors, musicians and photographers.

The redesigned MacBook Pro comes in two flavors: a 14-inch model and a 16-inch one, both loaded with ports. Aside from the aforementioned memory card slot, these machines also come with a built-in HDMI 2.0 port, Thunderbolt 4 ports, a 3.5mm headphone jack that supports high-end headphones and magnetic charging via MagSafe technology.