| xic | DIF Freedom Data |
| xid | Visual Localize XML Import Definition |
| xif | LonWorks Device Interface File |
| ximp | XOS Digital Export Package |
| xip | Photo Mechanic Metadata File |
| xir | XML Intermediate Representation Data |
| xit | SpatialAnalyzer Data |
| xit64 | SpatialAnalyzer Data |
| xix | Microsoft IIS NNTP Subject Lists |
| xjf | OmniPage BatchManager Job |
| xjsw | Tarsia Puzzle Data |
| xkb | X Keyboard Extension Data |
| xkm | X Keyboard Compiled Keymap Data |
| xkp | X-Keys Pro Data |
| xkt | Keysight Calibration Kit Data |
| xldb | XLerator Database |
| xle | XML Cooktop File |
| xlg | Autodesk AutoCAD XREF Log File |
| xlgc | Prosystech ExpressK Database |
| xli | 3D Studio Max IGES Input Log |
| xln | Excellon Drill File |
| xlo | 3D Studio Max IGES Output Log |
| xlo | Autodesk Inventor Export Journal |
| xlog | XLOG XML Log |
| xlp | SAP BO Xcelsius Add-On Package Project |
| xlsxenx | Egis Encrypted Powerpoint XLSX Template |
| xltbcd | XL Toolbox Chart Design Data |
| xlts | Umbraco Pro Data |
| xlx | SAP BO Xcelsius Add-On Package |
| xlz | Crossword Power Tools Crosswords Library |
| xmat | 3dDeconvolve Design Matrix |
| xmbl | Vernier Logger Pro Data |
| xmc | Expression Media Catalog |
| xmdl | XMDL Model |
| xmdx | ExamSoft SofTest Answer Data |