| xqa | PX Windows Board Description Data |
| xqcn | QPST Content |
| xqp | I-Doser Temporary Data |
| xqt | SuperCalc Macro |
| xqx | XQX Printer Stream Data |
| xr | Chaos Desktop Reference File |
| xrdml | PANalytical XRD Instruments Data |
| xrf | IMVU Material File |
| xri | XML for Requirements Interchange Data |
| xrio | OMICRON Test Universe Extended RIO Object |
| xrk | AiM Tech EVO4S Logger Data |
| xrl | OSCAR Rules Data |
| xrl | Rapidform XOR 3D Scan CAD Data |
| xrm-ms | Windows Vista Activation Certificate |
| xrnt | Renoise DSP Device-chains Data |
| xrt | Revolution Single-spectrum Xraytor Data |
| xry | XRY Data |
| xrz | AiM Tech EVO4S Logger Data |
| xs | Hummingbird Exceed Startup File |
| xsb | Sybase PowerDesigner XML Model Backup |
| xsb | XMLBeans XML Schema Binary |
| xsbz | Oracle BI Publisher Sub Template |
| xsc | RFM Molecule Cross-Section Data |
| xse | EQuIS Data Processor Format Definition Data |
| xseq | xLights Sequence Data |
| xsf | Xilinx CORE Generator Pin File |
| xsf | IMVU Skeleton Data |
| xsi | Softimage dotXSI 3D Model |
| xsig | eCoFirma XAdES Signature Data |
| xsk | XKeyBrew Menu Data |
| xsm | Sybase PowerDesigner XML Model |
| xso | XKeyBrew Menu Data |
| xsr | Bentley GEOPAK XS List Report |
| xssz | Oracle BI Publisher Style Template |
| xstb | TextBridge Pro Data |
