Editing Universal Disk Format (section)

== Usage ==
Normally, [[optical disc authoring software|authoring software]] will master a UDF file system in a batch process and write it to optical media in a single pass. But when [[packet writing]] to rewritable media, such as [[CD-RW]], UDF allows files to be created, deleted and changed on-disc just as a general-purpose [[filesystem]] would on removable media like [[floppy disk]]s and [[USB flash drive|flash drive]]s. This is also possible on write-once media, such as [[CD-R]], but in that case the space occupied by the deleted files cannot be reclaimed (and instead becomes inaccessible).

Multi-session mastering is also possible in UDF, though some implementations may be unable to read disks with multiple sessions.{{efn|Multi-session mastering has always been part of the UDF specification. See [UDF 2.01/6.10.1], though earlier documents were not very clear that the anchor offsets are specified to be from the last session.}}