| xso | XKeyBrew Menu Data |
| xsp | MAPublisher XSP Data Source |
| xsr | Bentley GEOPAK XS List Report |
| xssz | Oracle BI Publisher Style Template |
| xstb | TextBridge Pro Data |
| xsu | UNICOM Sample User XML Data |
| 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 |
| xtpl | XER Manager Template |
| xtr | XTrkCad Demo |
| xtreme | Winstep Xtreme Theme Pack |
| xtrl | XTND Translator Data |
| xts | IMPS Data |
| xtt | X TimeTable Data |
| xtxt | Xtext Data |
| xui | Xbox 360 User Interface Data |
| xur | Xbox 360 User Interface Binary Data |
| xus | UpdateStar Data |
| xvg | Grace Document |
| xvo | RatDVD Internal Data |
| xvp | XView Package |
| xvs | XView Scene Package |
