| xje | XJEase Source Code |
| xl | XBLite Source Code |
| xlist | MASM XLIST Data |
| xmcf | FileMaker Pro Custom Function Data |
| xmla | XML for Analysis File |
| xmljet | Eclipse JET XML Template |
| xmlo | FileMaker Pro Layout Object Data |
| xmta | Visual Studio Design-Time Attribute Data |
| xn | Cygwin LD-Script Data |
| xnb | XNA Game Studio Binary Package |
| xnd | exNode Download Data |
| xob | WeintekHMI EasyBuilder 8000 XOB File |
| xojo_menu | Xojo Menu Data |
| xojo_project | Xojo Project |
| xoml | Microsoft Visual Studio Windows Workflow |
| xpb | XPB! Basic Source Code |
| xpk | Xscript Package |
| xpp | X++ Source Code |
| xpz | GeneXus Object |
| xq | XQuery Language Source Code |
| xql | XML Query Language |
| xqm | Oxygen XML Editor XQuery Module |
| xqr | XQuery Language Source Code |
| xqu | XQuery Update Data |
| xquery | XQuery Language Source Code |
| xqy | XQuery Language Source Code |
| xrc | wxWidgets XML Based Resource |
| xrd | XRK Data File |
| xrg | Xscript Registry Data |
| xrm | XrmToolkit XRM Data |
