What is exFAT (and why is it on every SD card)?
In one sentence: A file system for memory cards and USB sticks that Windows, Macs, cameras and TVs can all read and write, with no 4 GB file limit but no safety journal either.
A little more
exFAT is a file system made for memory cards and USB sticks. It keeps the simple design of the old FAT32, a big table saying which blocks belong to which file, but drops FAT32's 4 GB limit on a single file, so long videos fit. It's the standard format for SD cards bigger than 32 GB, and Windows, Macs, Linux, cameras and most TVs and consoles can all read and write it, which is why it's the usual choice for a drive that moves between computers.
The trade-off is that exFAT has no journal. Formats like NTFS and APFS write a little note of what they're about to change before they change it, so they can tidy up after a sudden power cut. exFAT doesn't, so pulling a stick out mid-copy is more likely to damage a file or the table itself. That's why ejecting matters most on exactly the drives people share the most.
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