| xfsf | BestSync Settings Data |
| xgc | GtkRadiant XML Game Config |
| xgi | XBCD Custom Settings File |
| xgs | XACT Global Settings |
| xiu | Chiasmus Configuration |
| xjb | JAXB Binding Customization |
| xjs | Jindent Settings File |
| xlaunch | XLaunch Session Data |
| xlpf | Microsoft Excel for Mac Settings Data |
| xly | CMUD Settings Data |
| xmbclp | X-Mouse Button Control Data |
| xmbcs | X-Mouse Exported Settings Data |
| xml-prev | Oracle VM VirtualBox XML Settings Backup |
| xnote | XNote for Thunderbird Settings Data |
| xpadder | Xpadder Settings Data |
| xpaddercontroller | Xpadder Controller Profile Data |
| xpf | LMMS Presets Data |
| xpy | XPY Settings Data |
| xrx | Microsoft Expression Encoder Media Profile |
| xss | Sorenson Squeeze Presets Data |
| xvm | VMware Server Console Configuration |
| xwk | Crosstalk Communicator Keyboard Mapping |
| xwms | WMS Server Connection Data |
| xxe_gui | XMLmind XML Editor GUI Settings Data |
| yardopts | YARD Settings |
| ysm | Yamaha Studio Manager Settings Data |
| yt | yt Project Configuration |
| z7d | BlueZone ICL 7561 Display Settings Data |
| zaf | ZoneCentral Access List Data |
| zap | Windows Software Installation Settings |