| xpr | Pro/ENGINEER XPR File |
| xps | DB/TextWorks Exported Set Definitions |
| xpt | EES Export |
| xpu | IBM SiteProtector X-press Update File |
| xpw | Accessible FormNet Data File |
| xpx | Accessible FormNet Data File |
| xqp | I-Doser Temporary Data |
| xqt | SuperCalc Macro |
| xqx | XQX Printer Stream Data |
| xr | Chaos Desktop Reference File |
| xrdml | PANalytical XRD Instruments Data |
| xrf | IMVU Material File |
| xri | XML for Requirements Interchange Data |
| xrm-ms | Windows Vista Activation Certificate |
| xry | XRY Data |
| xs | Hummingbird Exceed Startup File |
| xsb | Sybase PowerDesigner XML Model Backup |
| xsb | XMLBeans XML Schema Binary |
| xsc | RFM Molecule Cross-Section Data |
| xsf | IMVU Skeleton Data |
| xsf | Xilinx CORE Generator Pin File |
| xsi | Softimage dotXSI 3D Model |
| xsig | eCoFirma XAdES Signature Data |
| xsm | Sybase PowerDesigner XML Model |
| xsr | Bentley GEOPAK XS List Report |
| xsvf | Xilinx Serial Vector Format |
| xsz | ZynAddSubFX Standalone Scale File |
| xtb | LocoScript External Translation Table |
| xtd | LabChip XT Data |
| xte | LabChip XTe Data |
| xtf | LS-DYNA Extra Time History Database |
| xtk | X-Ray Toolkit Metadata |
| xtm | XtremSplit Data |
| xtp | XTree Data |
| xtp | XTrkCAD Layout |
