| xml | Extensible Markup Language File |
| xmls | Microsoft Excel 2003 XML Document |
| xmn | Sprintometer Document |
| xmt | Romulus 3D Modeler Data |
| xod | Silverlight XPS Document |
| xoi | eZediaMX Locked Presentation Document |
| xov | Rapidform XOV 3D Model |
| xpdl | XML Process Definition Language Document |
| xpf | Homestead Sitebuilder Document |
| xpr3 | QuarkXPress for Mac Document |
| xps | XML Paper Document |
| xpwe | PriMus XML Exchange Document |
| xrw | Architag XRay XML Editor Document |
| xs3 | XESS Worksheet |
| xs4 | XESS Worksheet |
| xs5 | XESS Worksheet |
| xscscpt | Transcribe! Script |
| xsd | Microsoft InfoPath XML Schema |
| xsf | Microsoft InfoPath Form Definition |
| xsh | Xshade 3D Model |
| xsl | Extensible Stylesheet Language Transformations |
| xslt | Extensible Stylesheet Language Transformations |
| xsn | Microsoft InfoPath Form Template |
| xsslog | Microsoft SharePoint WorkSpace Groove Log Data |
| xssr | Microsoft SharePoint Workspace Data |
| xsx | Microsoft XML Schema Designer View |
| xtg | QuarkXPress Tags File |
| xtps | xTeam Document |
| xtrn | Call Report Pro XBRL Instance Document |
| xv0 | Extensible Virtual World Description Language Document |