| 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 |
| xvu | Comodo BOClean Definitions |
| xvv | Placevent 3D-RISM Results Data |
| xvw | MAPublisher View Data |
| xwav | eXtendable Wad Editor XWAV Data |
| xwz | X-Setup Pro Wizard Data |
| xx | Xxencoded Data |
| xxd | Brixx Planner Calendar Data |
| xxe | Xxencoded Data |
| xxi | GameSpy Arcade Data |
| xxl | Xilog Plus XXL File |
| xxs | StruMM3D Structure Data |
| xxx | Singer XL Embroidery Data |
| xya | ANUGA XYA Data |
| xyb | QuickWave 3D Batch List |
| xye | TOPAS Data |
| xyh | TunnelCAD Coordinate Data |
| xys | XYplorer Script |
| xyz | Celestia Trajectory File |
| xyz | Tinker Cartesian Coordinates |
| xyzc | Voxler 3D Geometry Data |
| xyznb | Exocad 3D Mesh Data |
| xyzv | Celestia v1.6 Trajectory File |
| xzp | Freestyle Dash Skin |
| x_b | Parasolid CAD Binary Parts Data |
| x_t | Parasolid CAD ASCII Parts Data |
| y01 | Corel Paradox Secondary Index |
| y02 | Corel Paradox Secondary Index |