| Extension | File Description |
| .UM7 | Uncommon Files |
| .UM8 | Uncommon Files |
| .UM9 | Uncommon Files |
| .UMA | Uncommon Files |
| .UMB | Uncommon Files |
| .UMC | Uncommon Files |
| .UMD | Uncommon Files |
| .UME | Uncommon Files |
| .UMF | Uncommon Files |
| .UMG | Uncommon Files |
| .UMH | Uncommon Files |
| .UMI | Uncommon Files |
| .UMK | Uncommon Files |
| .UMM | Uncommon Files |
| .UMN | Uncommon Files |
| .UMO | Uncommon Files |
| .UMP | Uncommon Files |
| .UMQ | Uncommon Files |
| .UMR | Uncommon Files |
| .UMT | Uncommon Files |
| .UMU | Uncommon Files |
| .UMV | Uncommon Files |
| .UMW | Uncommon Files |
| .UMY | Uncommon Files |
| .UMZ | Uncommon Files |
| .UN0 | Uncommon Files |
| .UN1 | Uncommon Files |
| .UN2 | Uncommon Files |
| .UN3 | Uncommon Files |
| .UN4 | Uncommon Files |
| .UN5 | Uncommon Files |
| .UN6 | Uncommon Files |
| .UN7 | Uncommon Files |
| .UN8 | Uncommon Files |
| .UN9 | Uncommon Files |
| .UNA | Uncommon Files |
| .UNASSIGNED | Uncommon Files |
| .UNB | Uncommon Files |
| .UNC | Uncommon Files |
| .UNCIAL | Uncommon Files |
| .UND | Uncommon Files |
| .UNE | Uncommon Files |
| .UNF | Uncommon Files |
| .UNG | Uncommon Files |
| .UNH | Uncommon Files |
| .UNIKEY | Uncommon Files |
| .UNION | Uncommon Files |
| .UNIVERSAL3 | Uncommon Files |
| .UNIX | Uncommon Files |
| .UNJ | Uncommon Files |
| .UNK | Uncommon Files |
| .UNLOCK | Uncommon Files |
| .UNM | Uncommon Files |
| .UNN | Uncommon Files |
| .UNO | Uncommon Files |
| .UNP | Uncommon Files |
| .UNPAC | Uncommon Files |
| .UNPACK | Uncommon Files |
| .UNQ | Uncommon Files |
| .UNS | Uncommon Files |
| .UNU | Uncommon Files |
| .UNUSED | Uncommon Files |
| .UNV | Uncommon Files |
| .UNW | Uncommon Files |
| .UNY | Uncommon Files |
| .UNZ | Uncommon Files |
| .UN_ | Uncommon Files |
| .UO0 | Uncommon Files |
| .UO1 | Uncommon Files |
| .UO2 | Uncommon Files |
| .UO3 | Uncommon Files |
| .UO4 | Uncommon Files |
| .UO5 | Uncommon Files |
| .UO6 | Uncommon Files |
| .UO7 | Uncommon Files |
| Extension | File Description |
| .UO8 | Uncommon Files |
| .UO9 | Uncommon Files |
| .UOA | Uncommon Files |
| .UOB | Uncommon Files |
| .UOC | Uncommon Files |
| .UOD | Uncommon Files |
| .UOE | Uncommon Files |
| .UOG | Uncommon Files |
| .UOH | Uncommon Files |
| .UOI | Uncommon Files |
| .UOJ | Uncommon Files |
| .UOK | Uncommon Files |
| .UOL | Uncommon Files |
| .UOM | Uncommon Files |
| .UON | Uncommon Files |
| .UOO | Uncommon Files |
| .UOP | Uncommon Files |
| .UOQ | Uncommon Files |
| .UOR | Uncommon Files |
| .UOS | Uncommon Files |
| .UOT | Uncommon Files |
| .UOU | Uncommon Files |
| .UOV | Uncommon Files |
| .UOW | Uncommon Files |
| .UOX | Uncommon Files |
| .UOY | Uncommon Files |
| .UOZ | Uncommon Files |
| .UP | Uncommon Files |
| .UP0 | Uncommon Files |
| .UP1 | Uncommon Files |
| .UP2 | Uncommon Files |
| .UP3 | Uncommon Files |
| .UP4 | Uncommon Files |
| .UP5 | Uncommon Files |
| .UP6 | Uncommon Files |
| .UP7 | Uncommon Files |
| .UP8 | Uncommon Files |
| .UP9 | Uncommon Files |
| .UPB | Uncommon Files |
| .UPC | Uncommon Files |
| .UPCASE | Uncommon Files |
| .UPDATEALL | Uncommon Files |
| .UPDATEINFO | Uncommon Files |
| .UPDATES | Uncommon Files |
| .UPDF | Uncommon Files |
| .UPE | Uncommon Files |
| .UPH | Uncommon Files |
| .UPI | Uncommon Files |
| .UPJ | Uncommon Files |
| .UPL | Uncommon Files |
| .UPM | Uncommon Files |
| .UPN | Uncommon Files |
| .UPO | Uncommon Files |
| .UPP | Uncommon Files |
| .UPQ | Uncommon Files |
| .UPS | Uncommon Files |
| .UPT | Uncommon Files |
| .UPU | Uncommon Files |
| .UPV | Uncommon Files |
| .UPW | Uncommon Files |
| .UPY | Uncommon Files |
| .UPZ | Uncommon Files |
| .UQ0 | Uncommon Files |
| .UQ1 | Uncommon Files |
| .UQ2 | Uncommon Files |
| .UQ3 | Uncommon Files |
| .UQ4 | Uncommon Files |
| .UQ5 | Uncommon Files |
| .UQ6 | Uncommon Files |
| .UQ7 | Uncommon Files |
| .UQ8 | Uncommon Files |
| .UQ9 | Uncommon Files |
| .UQA | Uncommon Files |
| .UQB | Uncommon Files |
| .UQC | Uncommon Files |
