| twrps | TWRP Settings |
| txr | CorelDRAW Graphics Custom Settings Data |
| typeit4me | TypeIt4Me Clippings |
| 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 |
| ucx | IronCAD Settings Data |
| udc | Universal Data Connection |
| udcx | Universal Data Connection |
| uec | UltraEdit Saved Settings |
| ufi | UFOCapture V2 Settings |
| uhv | Eurotherm 6100a Bridge Profile |
| 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 |
| userconfig | Weblogic Admin UserConfig Data |
| usr | EAGLE User-specific Parameters Data |
| utl | SAP BACKINT Interface Profile |
| uvksr | Ultra Virus Killer System Repair Settings Data |
| uvopt | µVision v4 Project Options |