| 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 |
| 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 |
| xltbcd | XL Toolbox Chart Design 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 |
| xme | GME Metamodel |
| xmef | TextMap Evidence Format Data |
| xmf | IMVU 3D Model |
| xmfa | Mauve eXtended Multi-FastA Data |
| xmi | XMVB Input File |
| xmldsig | XML Digital Signature |
| xmlr | SiteScan XML Results |
| xmlz | ZennoPoster MP Template Data |
| xmm | Autodesk 3D Studio MAX XML Animation Map |
| xmmap | MindManager XML Map |
| xmmas | MindManager XML Theme Data |
| xmmat | MindManager XML Template |
| xmo | XMVB Output File |