File extensions start with character 'X'
| File Type | Category | File Format | |
|---|---|---|---|
| .x32 | Adobe Files | Adobe Xtra File | |
| .xaf | 3D Graphics Files | 3ds Max XML Animation File | |
| .xaf | 3D Graphics Files | Cal3D XML Animation File | |
| .xaf | Data Files | Affirm Deposition Transcript | |
| .xap | Program Execution Files | Silverlight Application Package | |
| .xappl | Data Files | Spoon XML Application Configuration File | |
| .xas | Data Files | Pro/ENGINEER Assembly Instance Accelerator File | |
| .xbc | Data Files | SMART Notebook File | |
| .xbdoc | Text Files | Xiosis Scribe Document | |
| .xbe | Executable Files | Xbox Executable File | |
| .xbk | Backup Files | XenServer Backup File | |
| .xbk | Data Files | SMART Notebook File | |
| .xbplate | Text Files | Xiosis Scribe Template | |
| .xbt | Data Files | SMART Notebook Template File | |
| .xcappdata | Development Files | Xcode App Data File | |
| .xcf | Raster Graphics Files | GIMP Image File | |
| .xcworkspace | Development Files | Xcode Workspace File | |
| .xdb | Data Files | Symantec Virus Database File | |
| .xdl | Text Files | XML Schema File | |
| .xdp | Data Files | XML Data Package | |
| .xds | Game Files | DS Game Maker Project File | |
| .xdw | Page Layout Files | Fuji Xerox DocuWorks File | |
| .xef | Compressed Files | WinAce Encrypted File | |
| .xef | Data Files | eManager Form Data | |
| .xem | Data Files | PowerDesigner Model definition File | |
| .xer | Data Files | Primavera P6 Project File | |
| .xex | Game Files | Xbox 360 Executable File | |
| .xfd | Adobe Files | XFD File | |
| .xfd | Data Files | FormFlow 99 Form Data File | |
| .xfdf | Data Files | Adobe Acrobat XFDF File | |
| .xfdl | Web Files | XFDL File | |
| .xfo | Data Files | XSL-FO Formatted Form | |
| .xfr | Data Files | iProcess Process Definition File | |
| .xft | Data Files | Adobe Form Designer 5.0 File | |
| .xgml | Data Files | Graph Modeling Language XML File | |
| .xgmml | Data Files | XGMML Graph File | |
| .xif | Page Layout Files | ScanSoft Pagis File | |
| .xlc | Data Files | Excel Chart | |
| .xlf | Data Files | XLIFF Document | |
| .xlgc | Data Files | ExpressK Database File | |
| .xls | Spreadsheet Files | Excel Spreadsheet | |
| .xlsm | Spreadsheet Files | Excel Open XML Macro-Enabled Spreadsheet | |
| .xlsx | Spreadsheet Files | Microsoft Excel Open XML Spreadsheet | |
| .xlt | Data Files | Excel Template | |
| .xlw | Partially Downloaded Files | Excel Workspace File | |
| .xmb | Game Files | Age of Empires Game Data File | |
| .xmcd | Data Files | Mathcad Worksheet File | |
| .xmd | Disk Image Files | Extended Media Disc Image | |
| .xmi | Data Files | XML Metadata Interchange File | |
| .xml | XML Files | XML File | |
| .xmpz | Data Files | Miradi XML Project File | |
| .xnb | Game Files | XNA Game Studio Binary Package | |
| .xpdl | Data Files | XPDL Module | |
| .xpg | Data Files | Autoplay Media Studio Exported Page | |
| .xpi | Plug-in Files | Mozilla Installer Package | |
| .xpj | Data Files | RoboHelp HTML Project File | |
| .xpk | Game Files | WWE RAW Model File | |
| .xpr | 3D Graphics Files | Pro/ENGINEER Part Instance Accelerator File | |
| .xpr | Data Files | SyncRO Soft oXygen XML Editor Project | |
| .xpr | Vector Graphics Files | Microsoft Expression Design Graphic | |
| .xps | Page Layout Files | XML Paper Specification File | |
| .xpt | Plug-in Files | Mozilla Firefox Component | |
| .xpt | Data Files | SAS Transport File | |
| .xrff | Data Files | Extensible Attribute-Relation File Format | |
| .xrp | Data Files | RationalPlan Project File | |
| .xry | Data Files | XRY Data File | |
| .xsl | Data Files | XML Style Sheet | |
| .xsvf | Data Files | Xilinx Serial Vector Format File | |
| .xsx | Development Files | Visual Studio XML Schema Layout File | |
| .xt | Development Files | Xdebug Trace File | |
| .xtg | Data Files | Extensible TreeGraph File | |
| .xtm | Data Files | CmapTools Exported Topic Map | |
| .xtp | Configuration Files | AutoCAD Exported Tool Palettes File | |
| .xtp | Page Layout Files | InfoPath Template Part File | |
| .xvct | Data Files | VISE XML Project File | |
| .xwp | Text Files | XMLwriter Project | |
| .xxd | Data Files | Brixx Planner Calendar | |
| .xxx | Multiple Use Files | Compucon Singer Embroidery File | |
| .xy | Text Files | XYWrite Document | |
| .xy3 | Text Files | XYWrite III Document | |
| .xyp | Text Files | XYWrite Plus Document | |
| .xyw | Text Files | XYWrite for Windows Document | |
| .xyz | Data Files | Molecule Specification File | |
| .xyzv | Data Files | Celestia Sampled Trajectory File |