| xop | IGOR Pro Extension |
| xor | Xortool Results Data |
| xot | XGW Job Output Data |
| xpcm | X-Setup Pro Code Module |
| xpd | PlayStation Network Downloader Data |
| xpf | DB/TextWorks Exported Form Definitions |
| xpf | IMVU Morph Data |
| xpg | Autoplay Media Studio Exported Page |
| xpgt | Adobe InDesign XML Page Template File |
| xpk | NMRView Peak List |
| xpk | DB/TextWorks Exported Record Skeleton Definitions |
| 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 |
| xpt | EES Export |
| xpt | SAS XPORT Engine Data |
| xptheme | Theme Manager Theme Package |
| 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 |
| xrb | XMind Resource Bundle |
| xrb | GIS Web Template XML Resource Bundle |
| xrdml | PANalytical XRD Instruments Data |
| xresult | Xcode Xresult Data |
| xrf | IMVU Material File |
| xri | XML for Requirements Interchange Data |