| xpk | DB/TextWorks Exported Record Skeleton Definitions |
| xpk | NMRView Peak List |
| xpl | LcdStudio Playlist |
| xpo | Microsoft Dynamics AX Export |
| xport | SAS XPORT Engine Data |
| xpq | DB/TextWorks Exported Query Screen Definitions |
| xpr | Pro/ENGINEER XPR File |
| xps | DB/TextWorks Exported Set Definitions |
| xpse | KNFB Reader Data |
| xpt | EES Export |
| xpt | SAS XPORT Engine Data |
| xptheme | Theme Manager Theme Package |
| xptin | XPSWMM Hydrology Data |
| xpu | IBM SiteProtector X-press Update File |
| xpw | Accessible FormNet Data File |
| xpx | Accessible FormNet Data File |
| xqa | PX Windows Board Description Data |
| xqcn | QPST Content |
| xqp | I-Doser Temporary Data |
| xqt | SuperCalc Macro |
| xqx | XQX Printer Stream Data |
| xr | Chaos Desktop Reference File |
| xr2 | Xrecode II Registration Data |
| xr21 | Xrecode II Registration Data |
| xra | SPPAS Annotation Tool Data |
| xrb | OpenOffice JAVA Language Translation XML |
| xrb | XMind Resource Bundle |
| xrb | GIS Web Template XML Resource Bundle |
| xrdml | PANalytical XRD Instruments Data |
| xrds | eXtensible Resource Descriptor Sequence Data |
