The Free On-line Dictionary of Computing (19 January 2023):

Universal Disk Format
UDF

    (UDF) A CD-ROM file system standard
   that is required for DVD ROMs.  UDF is the OSTA's
   replacement for the ISO 9660 file system used on CD-ROMs,
   but will be mostly used on DVD.  DVD multimedia disks use
   UDF to contain MPEG audio and video streams.

   To read DVDs you need a DVD drive, the kernel driver for the
   drive, MPEG video support, and a UDF driver.  DVDs containing
   both UDF filesystems and ISO 9660 filesystems can be read
   without UDF support.

   UDF can also be used by CD-R and CD-RW recorders in
   packet writing mode.

   (1999-09-01)