| wvl | WorkView3D Links |
| wvw | Interleaf WorldView Document |
| wws | Writing With Symbols Document |
| wwt | Microsoft Works Template |
| wxmx | wxMaxima Document |
| wxp | EXP Document |
| wxs | Easy Cross stitch design |
| wyn | WYNN Document |
| wyx | WYNN Document |
| wzfolder | WhizFolders Document |
| wzn | WhizFolders Note Document |
| wzs | Microsoft Word Wizard |
| x3d | X3D Scene |
| x3db | X3D Binary Scene |
| x3dbz | Compressed X3D Binary Scene |
| x3dv | X3D Classic VRML |
| x3dvz | Compressed X3D Classic VRML |
| x3dz | Compressed X3D Scene |
| x3g | MakerBot X3G Document |
| xav | Final Draft AV v2 Document |
| xbc | SMART Notebook Document |
| xbd | Xerox DocuWorks Binder Document |
| xbdoc | Xiosis Scribe Document |
| xbel | XBEL Bookmark |
| xbk | SMART Notebook Document |
| xbmml | BMML File with Metadata |
| Braille Music Markup Language File |
| xbplate | Xiosis Scribe Template |
| xbrl | eXtensible Business Reporting Language |
| xbt | SMART Notebook Template |
| xcm | Concept Map |
| xddm | OpenVSP v2 VSP Design Document |
| xdes | OpenVSP VSP Design Document |
| xdoc | QuarkXPress 3.0 Document |
| xdot | Graphviz DOT File |
| xdp | XML Data Package |
| xdr | XML-Data Reduced Schema |
| xdv | XeTeX Extended DVI Document |
| xdw | Xerox DocuWorks Document |
| xfa | XML Forms Architecture Document |
| xfd | XFDL Document |
| xfdf | Adobe Acrobat XFDF Document |
| xfdl | XFDL Document |
| xfo | XSL-FO Formatted Form |
| xfp | Microsoft InfoPath Property Promotion |
| xgl | XGL 3D CAD Model |
| xgml | Graph Modeling Language XML |
| xgz | MegaBitz XGL Vector Drawing |
| xhf | XHeader Document |
| xht | XHTML Document |
| xhtm | XHTML Document |
| xhtml | XHTML Document |
| xig | XML Instance Generator Document |
| xl | Microsoft Excel Worksheet |
| xla | Microsoft Excel VBA Add-in |
| xla8 | Microsoft Excel 98 for Mac Add-in |
| xlam | Microsoft Excel 2007 VBA Add-in |
| xlax | Microsoft Excel 2007 VBA Add-in |
| xlb | Microsoft Excel toolbar Setup |
| xlc | Microsoft Excel Chart File |
| xlc3 | Microsoft Excel 3 for Mac Chart Document |
| xlc4 | Microsoft Excel 4 for Mac Chart Document |
| xlcsv | Microsoft Excel Comma-Separated Values Document |
| xld | Microsoft Excel Dialogue |
| xlf | XLIFF Document |
| xli | XLIFF Document |
| xlif | XLIFF Document |
| xliff | XLIFF Document |
| xline | XLine Mind Map Document |
| xlk | Microsoft Excel XLS Backup |
| xll | Microsoft Excel Add-in |
| xlm | Microsoft Excel Macro Definition |
| xlm4 | Microsoft Excel 4 for Mac Macro Data |
| xlr | Microsoft Works Spreadsheet |
| xls | Microsoft Excel Worksheet |
| xls3 | Microsoft Excel 3 for Mac Document |
| xls4 | Microsoft Excel 4 for Mac Document |
| xls5 | Microsoft Excel 5 for Mac Document |
| xls8 | Microsoft Excel 98 for Mac Document |
| xlsb | Microsoft Excel 2007 Document |
