I have bought a couple of USB micro SD card readers. I have bought a couple of micro SD memories. None of them work well. The shop has told me that computers have a maximum memory allowed.

I have not found anything like that anywhere. Is there a maximum memory allowed? It depends upon the computer? It depends upon the reader? Maybe it is just that the three micro SD memories where corrupted?

By the way, I have formatted the micro sd memory with the following tool:https://www.sdcard.org/downloads/formatter_4/ (OSX seems to be problematic to format because the compatibility with other devices. This association - software promises to solve that issue).


There is an excellent Support Article on Apple's website that addresses this: About the SD and SDXC card slot

Does the SD slot work with cards that exceed 32 GB?

Yes. However, most media manufactures preformat the media using common block-and-cluster sizes that do not approach the theoretical limits of a given file system. Most SD cards use the FAT32 file format. Preformatted FAT32 SD media is commonly available up to a capacity of 32 GB. Media that exceeds 32GB usually uses the exFAT file system. Some smaller capacity cards use the FAT16 file format. Preformatted FAT16 media is generally available up to a capacity of 2 GB. To determine which file system you are using with Mac OS X v10.6.5 or later, insert the media into the SD card slot, go to the Apple menu, select About this Mac..., click on More info..., click on Card Reader in the hardware section, and locate the File System field.

Which SD card formats work in the SD card slot?

Cards that conform to the SD 1.x, 2.x, and 3.x standards should work. The SD card slot can use cards that are Standard SD (Secure Digital) 4 MB to 2 GB, SDHC (Secure Digital High Capacity) 4 GB to 32 GB, and SDXC (Secure Digital Extended Capacity) 4G B to 2 TB. MMC can also be used in this slot. MiniSD, MicroSD, and higher density formats like MiniSDHC and MicroSDHC can also work with the use of "passive" adapters that conform to the width and thickness specifications listed above.

(Emphasis mine)

To format your SD card, you should use Disk Utility either using the GUI or via Terminal.

Using Terminal:

diskutil eraseDisk HFS+ DiskName GPT /dev/diskN


  • HFS+ = type of filesystem
  • DiskName = Name you want to give the SD card (i.e. "Stuff", "My Photos")
  • GPT = partition type
  • diskN = disk identifier (i.e disk4, disk7, etc.)

For more details, see man diskutil

  • Did you say 2TB SD card? Wowzers – MicroMachine Jan 10 '17 at 17:37
  • Not me...but Apple! I just report the news! – Allan Jan 10 '17 at 17:47
  • So in short as the most common formatting option is FAT32 the conclusion is: a SD memory above 32Gb will work only if 2 conditions apply: it has been formatted as exFAT or NTFS and it's SDXC (Secure Digital Extended Capacity). Does it also apply for USB readers of SD cards? – chelder Jan 10 '17 at 21:56

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