SD slot on MacBook Pro doesn't work

Does it work faster if you try to view the card in Image Capture, an app included with macOS?

Transfer images in Image Capture on Mac - Apple Support

Some camera cards have proprietary formatting/partitioning that the macOS cannot directly read . You need a translator. The often-complicated path to translation is to download and install the image management software that your camera's maker provides. The easy way is Image Capture.

Grant Bennet-Alder wrote:

Apple specs refer to that slot as the 'SDXC slot'.

¿Are you using cards at least that fast?

SDXC is not a speed rating. It refers to a capacity standard. SD cards have capacities of "up to 2 GB". SDXC cards have capacities of "more than 32 GB; up to 2 TB." The SDXC card reader in that MacBook Pro would be able to read SD cards, SDHC cards, or SDXC cards – but not SDUC ones.

SD Association – Capacity

For card and reader speeds, the appropriate references would be

SD Association – Speed Class

SD Association – Application Performance Class

SD Association – Bus Speed (Default Speed/High Speed/UHS/SD Express)

Apple specs refer to that slot as the 'SDXC slot'.

¿Are you using cards at least that fast?

if not the slowness may be caused by the CARD speed, not the Mac speed.

Use the SD and SDXC card slot on your Mac - Apple Support

"Your SDXC card slot supports the following cards: 

• MMC
• Default Speed
• High Speed
• UHS-I
• UHS‑II (Mac Studio introduced in 2022 or later, MacBook Pro introduced in 2021 or later, iMac introduced in 2020, and iMac Pro only)"

SDXC slot performance - Apple Community

A post here by the Level 9 user "neuroanatomist" says that "The rated speed for the internal slot is 250 MB/s for a UHS-II card and 90 MB/s for a UHS-I card (both of which are a bit slower than the UHS speed ratings of 312 and 104, respectively)."

I'm not sure where the ratings come from – if Apple has a Support article that lists those speeds, or if these were speeds that users discovered by doing benchmark testing.

"SD slot on MacBook Pro doesn't work: [...]When my SD card was plugged into the test macBook Pro, the card uploaded albeit not as fast as you would expect from Apple's new chip.[...]"

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Reading these Cards:

A. Adapter or PC:

If you need to obtain the data, then use an external adapter(iffy), or plug it into a PC.

B. Ask the Manufacturer:

Digging into this, what does the manufacturer have to say on this? Contact them, and see if there is a Serial Number or model number on the drive to provide them with. Ask them what Mac compatibility comments they have to say on this.