| xdf | XCAP Diff Data |
| xdfl | eXtensible Data Flow Language Document |
| xdfz | Compressed Extensible Data Format File |
| xdoclet | JBoss XDoclet Reference Data |
| xds | OpenGL Performer Script |
| xdt | Xscript Data File |
| xfd | Microfocus Acu4GL Extended Description |
| xfdl | XPLATFORM Screen Form Definition |
| xfl | Adobe Flash Exchange Data |
| xgdw | GDevelop Extension |
| xgf | Xgridfit Program |
| xgm | Exient XGS Model Data |
| xgr | GraphEdit Filter Graph Markup Language |
| xgt | Exient XGS Texture Data |
| xib | Apple Interface Builder Development-Time Resources |
| xil | Xilize Markup Source |
| xilinc | Xilize Include |
| xilize | Xilize Configuration Data |
| xin | OmniMark Include File |
| xiw | CSR µEnergy SDK Workspace |
| xjb | OEPE JAXB Wizard Bindings Data |
| xje | XJEase Source Code |
| xl | XBLite Source Code |
| xlc | Exient XGS Locale Data |
| xlist | MASM XLIST Data |
| xmap | CodeWarrior Linker Map Data |
| xmat | Exient XGS Shader Material Data |
| xmcf | FileMaker Pro Custom Function Data |
| xmf | Milinta APL Mainframe SAM Data |
| xmla | XML for Analysis File |
