| xcsr | Oracle UCM Content Folio XML |
| xcst | Oracle UCM Content Folio Template |
| xcworkspace | Xcode Workspace Data |
| xdat | XMVB Data File |
| xdb | Norton Antivirus Update |
| xdd | XFIT XDD Format Data |
| xdelta | Xdelta Binary Differential Data |
| xdf | TunerPro Definition File |
| xdl | Expert Definition Language Document |
| xdm | Oracle BI Publisher Data Model |
| xdmz | Oracle BI Publisher Compressed Data Model |
| xdna | DNA Strider Sequence Data |
| xdo | Oracle BI Publisher Report Definition |
| xdoz | Oracle BI Publisher Compressed Report Definition |
| xdrz | Oracle BI Publisher Folder Data |
| xds | LcdStudio Design |
| xec | Afaria XEC File |
| xed | Kinect Studio Recording |
| xef | X-Genics eManager Form Data |
| xej | Microsoft Expression Encoder Job |
| xel | Microsoft Expression Encoder Live Encoding |
| xem | Sybase PowerDesigner Extension File |
| xensearch | XenCenter Saved Search |
| xeq | Sage MAS 90 XEQ Data |
| xes | X-Genics eManager Skin Data |
| xet | X-Genics eManager Process Definition |
| xev | X-Genics eManager Auto-Update File |
| xevgenxml | Internet Explorer XEV GenericApp |
| xez | X-Genics eManager Template Package |
| xf | Scanalyze Transform Data |
| xfb | LonWorks Binary Device Interface File |
| xfc | Origin Compiled X-Function File |
| xff | NiceLabel Form Data |
| xfg | FACSGen Face Data |
| xfi | xICE Desktop Encrypted Data |