.U | Epic Games | Pelitiedostot | Unreal Tournament Class Package | Microsoft Windows Media Player | Microsoft Corporation |
.UBS | Microsoft Corporation | Harvinaiset Tiedostot | Tracesrv Bugslayer Utility File | Tracesrv Bugslayer Windows Utility Software | Microsoft Corporation |
.UCCAPILOG | Microsoft Corporation | Datatiedostot | Microsoft UCC API Log File | Microsoft Windows Live Messenger | Microsoft Corporation |
.UCE | Microsoft Corporation | Järjestelmätiedostot | Windows UCE System File | Microsoft Windows | Microsoft Corporation |
.UDF | Open Source | Levyn kuvatiedostot | Universal Disk Format Image File | Microsoft Excel | Microsoft Corporation |
.UG | Autodesk, Inc. | Vektorikuvatiedostot | Drawing File | ACD Systems Canvas | Microsoft Corporation |
.UGA | Microsoft Corporation | Datatiedostot | Ulead GIF Animator File | GIF Animator | Microsoft Corporation |
.UH | Ensemble Studios | Pelitiedostot | Age Of Empires II (The Age Of Kings) File | Age of Empires II | Microsoft Corporation |
.UL | Microsoft Corporation | Asetustiedostot | Windows Updates Downloader Update List File | Windows Updates Downloader | Microsoft Corporation |
.ULS | Microsoft Corporation | Datatiedostot | NetMeeting User Location Service File | Microsoft NetMeeting | Microsoft Corporation |
.ULZ | Microsoft Corporation | Asetustiedostot | Windows Updates Downloader Update List File | Windows Updates Downloader | Microsoft Corporation |
.UMB | Microsoft Corporation | Asetustiedostot | MemMaker Backup Archive | MS-DOS | Microsoft Corporation |
.UMF | GetMediaHolder.com | Datatiedostot | MediaHolder Universal Media Format File | Microsoft Notepad | Microsoft Corporation |
.UPD | Various Developers | Tekstitiedostot | Program Update Information | Microsoft Notepad | Microsoft Corporation |
.UPS | Open Source | Pelitiedostot | UPS Patch File | Microsoft Works | Microsoft Corporation |
.URI | Microsoft Corporation | Datatiedostot | List Of Uniform Resource Identifiers | Microsoft Notepad | Microsoft Corporation |
.URL | Microsoft Corporation | Web-tiedostot | Internet Shortcut | Microsoft Notepad | Microsoft Corporation |
.USA | Microsoft Corporation | Datatiedostot | American English Localization Language File | Microsoft Notepad | Microsoft Corporation |
.USE | Unknown Developer | Tekstitiedostot | Log File | Microsoft Notepad | Microsoft Corporation |
.USER | Microsoft Corporation | Asetustiedostot | Visual Studio Project User Options File | Microsoft Notepad | Microsoft Corporation |
.USF | EVGA Corporation | Asetustiedostot | EVGA Precision X Skin File | Microsoft Notepad | Microsoft Corporation |
.USR | FileMaker Inc. | Tietokantatiedostot | FileMaker Pro Database File | Microsoft Notepad | Microsoft Corporation |
.UTB | Unknown Developer | Varmuuskopiointitiedostot | µTBackup Backup | Microsoft Flight Simulator | Microsoft Corporation |
.UTXT | Open Source | Tekstitiedostot | Unicode Text File | Microsoft Notepad | Microsoft Corporation |
.UVU | Microsoft Corporation | Datatiedostot | Movie Maker Video Data | Microsoft Windows Live Movie Maker | Microsoft Corporation |
.UXDC | Microsoft Corporation | Datatiedostot | Microsoft Excel Data Retrieval Service Connection File | Microsoft Excel | Microsoft Corporation |