Why is it the only truly universal filesystem is FAT? The Univeral Disk Format is supposed to be universal, and in a sense it is - it's supported (at least read-only) by all the major operating systems. But can I format a disk UDF and use it on any of the major operating systems flawlessly? No! (Grrr...) In fact Linux seems to be the only OS that supports UDF in any form other than on a DVD or a CD-RW. Hooray for Linux but that still means that the only truly universal disk format is FAT.