File extensions beginning with u

File Extension Description
U3D Model file format
U3D Universal 3D
U8 Sample
UB Raw Unsigned Byte (8bit) data
UC2 Archive
UCN New archive
UCS Unknownsoft Service Pack (mainly for Shadow OS 2009)
UDF Filter
UDIWWW bookmark data
UDO Data
UDW Raw Unsigned DWord data
UE2 Encrypted archive
UFI data
UFO graphic file
UHA UHarc archive
UHS Universal Hint System (binary file)
UI Espire source code file
UI Qt Designer's UI File
UI User interface
UIF Long prompts for windows
UIH Espire header file
UL ULAW audio file
ULD Information about uploaded files
ULF data
ULT Music
UMB Backup file
UNF Universal NES Image Interchange File Format
UNI Datafile
UNI Music format
UNIF Universal NES Image Interchange File Format
UNX Text file containing UNIX specific info
UOML UniqueObject Markup Language (UOML) is a XML-based markup language
UOP Uniform Office Format presentation
UOS Uniform Office Format spreadsheet
UOT Uniform Office Format text
UPD Update data
UPO Compiled update data
URL Internet Shortcut (URL)
URT Utah Raster Toolkit
USE Log file
USP Printer font with USASCII extended character set
USR User database file
UT! datafile
UTZ Mobile Phone Theme
UU Encoded file (ASCII)
UUE Encoded file (ASCII)
UW Raw Unsigned Word 16bit data
UWF UltraTracker WaveSample