| Extension | Description | File Type |
|---|
| x | DirectX Object File | 3D Files |
| x32 | Adobe Xtra File | 3D Files |
| x64 | Commodore 64 Disk Image File | Disk Image Files |
| xap | Silveright Application Package | Web Files |
| xbel | XML Bookmark Exchange Language File | Web Files |
| xcf | Gimp Image File | Graphic Files |
| xdw | X Windows Screen Dump File | Graphic Files |
| xex | Xbox 360 Executable File | Executable Files |
| xfdl | Extensible Forms Description Language File | Web Files |
| xhtml | Extensible HyperText Markup Language File | Web Files |
| xlr | Microsoft Works Spreadsheet File | Spreadsheet Files |
| xls | Excel Spreadsheet File | Spreadsheet Files |
| xlsm | Microsoft Excel Macro-enabled Workbook file | Spreadsheet Files |
| xlsx | Microsoft Excel XML File | Data Files |
| xmcd | Mathcad Worksheet File | Game Files |
| xmf | Gamejack Disk Image File | Disk Image Files |
| xml | Extensible Markup Language | Data Files |
| xmp | Extensible Metadata Platform | Misc Files |
| xp3 | TVP XPK3 Virtual File System File | Game Files |
| xpi | XPInstall File | Archived Files |
| xps | XML Paper Specification File | Layout Files |
| xpt | Mozilla Firefox Component File | Web Files |
| xs | Age Of Empires III Map AI Generator File | Game Files |
| xsd | XML Schema File | Developer Files |
| xspf | XML Shareable Playlist File | Audio Files |
| xtm | Xtremsplit Data File | Data Files |
| xtreme | Winstep Theme Pack File | Misc Files |
| xul | XML User Interface Language File | Developer Files |
| xv | Khoros VIFF Bitmap File | Graphic Files |
| xvid | Xvid Video File | Video Files |
| xxx | Singer Embroidery File | Misc Files |
| xz | XZ Compressed Archive | Archived Files |