UDF, or the Universal Disc Format, is the primary filesystem that is used on DVD media and, to a lesser extent, CD-RW discs for Packet Writing. It is based on the ISO 13346 standard, and is now currently in version 2.0.1.

The main virtues of the UDF system include native unicode support, virtually unlimited path lengths (versus 31 characters for HFS/HFS+, 63 characters for ISO 9660 and Joliet, and 128 characteres for Romeo), and a whopping large storage size -- something in the terabyte range, if memory serves.