The answer is it depends. I can't speak from the device side, since I'm not going to open up my tablet.
SD -> pre-formatted FAT.
SDHC -> pre-formatted FAT32
SDXC -> pre-formatted exFAT or FAT32.
Officially / legally to support exFAT, you must get a license from Microsoft.
Most devices support FAT32 but not exFAT.
Windows (at least XP) won't format things to FAT32 over a certain size, 32GB if I remember correctly.
exFAT has the advantage that it has higher limits, such as storing files over 4GB - 1 byte, which might be desirable for many 64GB / UHS-I card users as the emphasis is pretty much on recording a real time stream of full HD video and you don't always want to start a new file every couple gigs.
To further complicate matters the Android ROM (e.g. TouchWiz) does not support mounting all file systems the kernel is capable of supporting. So for example, most devices can mount FAT formatted cards but not ext4 formatted, despite the internal memory using ext4!
These are software issues.
In order to use certain "Newer" features of modern SD cards: you need to have hardware support for additional pins and signalling, including any 'reassigned' pins. Pins, as in those things on the end of the card that you plug in. An example of said newer hardware features are things like Ultra High Speed (UHS) for faster transfer rates. Some hardware may also be physically capable of these features but be loaded with firmware that does not support these features or is lacking some necessarily licensing data to enable the associated behaviour.
Our device supports the following file systems:
$ cat /proc/filesystems
So all Microsoft FAT should work unless the ROM gets modded to reject!
- Samsung Galaxy S3 (T-Mobile )SGH-T999, stock+rooted.
- ASUS Transformer TF201 32GB, CyanogenMod.
- ASUS Transformer TF101 32GB, Prime ROM (damaged/retired).
- HTC MyTouch 4G Slide, CM 9.1-stable, retired.
- HTC MyTouch 4G, my first CyanogenMod (7.1), sold.
- LG Optimus T, stock+rooted. gifted to a beautiful Firefly.