| 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 |
| xmod | Monarch Pro Model |
| xmp | Darktable Sidecar Data |
| xmps | FICO Xpress Optimizer Matrix Data |
| xmpses | Adobe Premiere Elements Chapter Point Information |
| xmpskin | XMPlay Skin Data |
| xmptf | TextMap Portable Transcript Data |
| xmp_bin | Parasolid CAD Binary Partition Data |
| xmp_txt | Parasolid CAD ASCII Partition Data |
| xmt_bin | Parasolid CAD Binary Parts Data |
| xmt_txt | Parasolid CAD ASCII Parts Data |
| xmu | eXtendable Wad Editor Data |
| xmx | Autodesk AutoCAD External Message File |
| xmzx | ExamSoft SofTest Exam Data |
| xnf | Extensible Numerical File Format Data |
| xng | FishXing Data |
| xnt | QuarkXPress Extension |
| xnv | nVision Layout |
| xo | Sugar Linux Application Bundle |
| xoj | Xournal Journal Data |
| xop | IGOR Pro Extension |
| xop | XML-Binary Optimized Packaging Data |
| xor | Xortool Results Data |
| xot | XGW Job Output Data |
| xpcm | X-Setup Pro Code Module |
| xpd | PlayStation Network Downloader Data |
| xpf | DB/TextWorks Exported Form Definitions |
| xpf | IMVU Morph Data |
| xpg | Autoplay Media Studio Exported Page |
| xpgt | Adobe InDesign XML Page Template File |
| xpk | NMRView Peak List |