Universal Disk Format

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Universal Disk Format (UDF) is an implementation of the specification known as ISO/IEC 13346 and ECMA-167 and is an open vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design, it is very well suited for incremental updates on both recordable or (re)writable optical media. UDF is developed and maintained by the Optical Storage Technology Association (OSTA).

Normally, 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 rewriteable 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 disks and flash drives. 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.[1]



The Optical Storage Technology Association standardized the UDF file system to form a common file system for all optical media. The goal was to make a common file system for read-only media and optical media that are re-writable. When first standardized, the UDF file system was intended to replace ISO-9660, allowing support for both read-only and writable media. After the first version of UDF was released, it was adopted by the DVD Consortium as the official file system for DVD Video and DVD Audio.[2]

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