| wztheme | WinZip Theme Data |
| x00 | Paradox Secondary Index |
| x01 | Paradox Secondary Index |
| x02 | Paradox Secondary Index |
| x03 | Paradox Secondary Index |
| x04 | Paradox Secondary Index |
| x05 | Paradox Secondary Index |
| x06 | Paradox Secondary Index |
| x07 | Paradox Secondary Index |
| x08 | Paradox Secondary Index |
| x09 | Paradox Secondary Index |
| x1 | X1 Saved Search |
| x1s | X1 Search Saved Search |
| x36 | Xplorer360 Data |
| x3p | XML 3D Surface Profile |
| x3s | X3S Data |
| x61 | Lenovo ThinkPad X61 Bios Update |
| x7a | Yamaha MONTAGE Backup Data |
| x7b | Yamaha MONTAGE Bulk Data |
| x83 | GAEB DA XML Data File |
| xa | Chiron NRG Exported Dictionary |
| xac | GnuCash Data |
| xac | XMetaL Author Customization File |
| xadd | Microsoft Expression Web Add-in |
| xades | XAdES Signature |
| xadml | XML-Based Application Description Information |
| xaf | Autodesk 3D Studio MAX XML Animation |
| xaf | IMVU Animation |
| xaiml | XAIML Chatterbot Database File |
| xao | SALOME Geometry XAO Data |
| xas | Pro/ENGINEER XAS File |
| xbb | DVIPDFMx Output File |
| xbckl | ApSIC Xbench Checklist Data |
| xbd | Xilinx Xilinx Board Description Format File |
| xbdr | Darkroom Booth Template |