Container file used by MediaHolder, an application used to download multimedia files and eBooks; stores metadata in addition to the multimedia content; may store information for the author, included file types, and hyperlink references; used as the format for downloading OnRead.com eBooks, but can be used for other types of data as well.

The UMF format enables split multimedia files to be downloaded in fragments. It also allows downloaded multimedia data to be categorized by the metadata stored in the UMF files. NOTE: The term "universal" refers to the fact that MediaHolder can store many types of multimedia in a UMF file. It does not refer to a file format that is ubiquitous and recognized by many applications, since only MediaHolder supports UMF files.