| tzi | Windows CE Time Zone Information |
| uae | WinUAE Configuration |
| uav | OpenPilot UAV Settings Data |
| ubb | BEA eLink Adapter Configuration |
| ubr | Web Capacity Analysis Tool Settings |
| uchr | Apple iOS Keyboard Layout |
| ucp | SmartWare Communications Profile |
| udc | Universal Data Connection |
| udcx | Universal Data Connection |
| uec | UltraEdit Saved Settings |
| ufi | UFOCapture V2 Settings |
| umb | MemMaker Configuration Backup File |
| umprofile | UltraMon Display Profile |
| unit | Systemd Unit Data |
| uns | Visual Navigation Suite Export Settings |
| upf | Bentley MicroStation User Preference File |
| upload | WebSTAR File Upload Option |
| upp | Unified Printer Parameter |
| upv | UniversalPlantViewer Configuration Data |
| usc | USC Module Definition |
| utl | SAP BACKINT Interface Profile |
| uvopt | µVision v4 Project Options |
| uvoptx | µVision v5 Project Options |
| ux | XMetaL XML Configuration File |
| v22 | V-22 Controller Settings Data |
| vbox | Oracle VM VirtualBox VM Settings |
| vbox-prev | Oracle VM VirtualBox VM Settings Backup |
| vbx6settings | VirusBarrier X6 Settings |
| vcfg | Microsoft Lync Voice Routing Configuration |
| vcl | Varnish Configuation Language File |
| vcomps | V-Comp Setup |
| vgr | Voyager Settings File |
| vgw | Sybase ASE VGW File |
| vimrc | Vim Runtime Configuration |
| vio | VIMNet Explorer Configuration |