| Extension | File Description |
| .URT | Raster Image Files |
| .URU | Uncommon Files |
| .URV | Uncommon Files |
| .URW | Uncommon Files |
| .URX | Uncommon Files |
| .URY | Uncommon Files |
| .URZ | Uncommon Files |
| .US | Uncommon Files |
| .US0 | Uncommon Files |
| .US1 | Uncommon Files |
| .US2 | Uncommon Files |
| .US3 | Uncommon Files |
| .US4 | Uncommon Files |
| .US5 | Uncommon Files |
| .US6 | Uncommon Files |
| .US7 | Uncommon Files |
| .US8 | Uncommon Files |
| .US9 | Uncommon Files |
| .USA | Game Files |
| .USAGE | Uncommon Files |
| .USB | Uncommon Files |
| .USC | Uncommon Files |
| .USD | Uncommon Files |
| .USE | Uncommon Files |
| .USER | Settings Files |
| .USERPROFIL | Settings Files |
| .USF | Audio Files |
| .USG | Uncommon Files |
| .USH | Uncommon Files |
| .USI | Uncommon Files |
| .USJ | Uncommon Files |
| .USK | Uncommon Files |
| .USL | Uncommon Files |
| .USM | Uncommon Files |
| .USN | Uncommon Files |
| .USO | Uncommon Files |
| .USP | Uncommon Files |
| .USQ | Uncommon Files |
| .USR | Database Files |
| .USS | Uncommon Files |
| .UST | Uncommon Files |
| .USTAR | Data Files |
| .USU | Uncommon Files |
| .USV | Uncommon Files |
| .USW | Uncommon Files |
| .USX | Game Files |
| .USY | Uncommon Files |
| .USYM | Uncommon Files |
| .USZ | Uncommon Files |
| .UT0 | Uncommon Files |
| .UT1 | Uncommon Files |
| .UT2 | Game Files |
| .UT2MOD | Game Files |
| .UT3 | Game Files |
| .UT4 | Uncommon Files |
| .UT4MOD | Game Files |
| .UT5 | Uncommon Files |
| .UT6 | Uncommon Files |
| .UT7 | Uncommon Files |
| .UT8 | Uncommon Files |
| .UT9 | Uncommon Files |
| .UTA | Uncommon Files |
| .UTB | Uncommon Files |
| .UTC | Game Files |
| .UTD | Uncommon Files |
| .UTE | Uncommon Files |
| .UTF | Uncommon Files |
| .UTG | Uncommon Files |
| .UTH | Uncommon Files |
| .UTI | Uncommon Files |
| .UTIL | Uncommon Files |
| .UTIL2 | Uncommon Files |
| .UTILITIES | Uncommon Files |
| .UTILITY | Uncommon Files |
| .UTILS | Uncommon Files |
| Extension | File Description |
| .UTJ | Uncommon Files |
| .UTK | Uncommon Files |
| .UTL | Uncommon Files |
| .UTM | Uncommon Files |
| .UTMP | Uncommon Files |
| .UTN | Uncommon Files |
| .UTO | Uncommon Files |
| .UTP | Uncommon Files |
| .UTQ | Uncommon Files |
| .UTR | Uncommon Files |
| .UTS | Uncommon Files |
| .UTT | Uncommon Files |
| .UTU | Uncommon Files |
| .UTV | Uncommon Files |
| .UTW | Game Files |
| .UTX | Game Files |
| .UTXT | Text Files |
| .UTY | Uncommon Files |
| .UTZ | Settings Files |
| .UU | Encoded Files |
| .UU0 | Uncommon Files |
| .UU1 | Uncommon Files |
| .UU2 | Uncommon Files |
| .UU3 | Uncommon Files |
| .UU4 | Uncommon Files |
| .UU5 | Uncommon Files |
| .UU6 | Uncommon Files |
| .UU7 | Uncommon Files |
| .UU8 | Uncommon Files |
| .UU9 | Uncommon Files |
| .UUA | Uncommon Files |
| .UUB | Uncommon Files |
| .UUC | Uncommon Files |
| .UUCP | Uncommon Files |
| .UUD | Encoded Files |
| .UUE | Encoded Files |
| .UUF | Uncommon Files |
| .UUG | Uncommon Files |
| .UUH | Uncommon Files |
| .UUI | Uncommon Files |
| .UUJ | Uncommon Files |
| .UUK | Uncommon Files |
| .UUL | Uncommon Files |
| .UUM | Uncommon Files |
| .UUN | Uncommon Files |
| .UUO | Uncommon Files |
| .UUP | Uncommon Files |
| .UUQ | Uncommon Files |
| .UUR | Uncommon Files |
| .UUS | Uncommon Files |
| .UUT | Uncommon Files |
| .UUU | Uncommon Files |
| .UUV | Uncommon Files |
| .UUW | Uncommon Files |
| .UUX | Uncommon Files |
| .UUY | Uncommon Files |
| .UUZ | Uncommon Files |
| .UV | Uncommon Files |
| .UV0 | Uncommon Files |
| .UV1 | Uncommon Files |
| .UV2 | Uncommon Files |
| .UV3 | Uncommon Files |
| .UV4 | Uncommon Files |
| .UV5 | Uncommon Files |
| .UV6 | Uncommon Files |
| .UV7 | Uncommon Files |
| .UV8 | Uncommon Files |
| .UV9 | Uncommon Files |
| .UVA | Audio Files |
| .UVB | Uncommon Files |
| .UVC | Uncommon Files |
| .UVD | Data Files |
| .UVE | Uncommon Files |
| .UVF | Data Files |
| .UVG | Raster Image Files |
