| xqx | XQX Printer Stream Data |
| xr | Chaos Desktop Reference File |
| xr2 | Xrecode II Registration Data |
| xr21 | Xrecode II Registration Data |
| xra | SPPAS Annotation Tool Data |
| xrb | GIS Web Template XML Resource Bundle |
| xrb | OpenOffice JAVA Language Translation XML |
| xrb | XMind Resource Bundle |
| xrdml | PANalytical XRD Instruments Data |
| xrds | eXtensible Resource Descriptor Sequence Data |
| xref | IBM AIX Cross Reference Data |
| xresult | Xcode Xresult Data |
| xrf | Cal3D XML Materials Data |
| xrf | IMVU Material File |
| xrff | Weka eXtensible Attribute-Relation File Format Data |
| xri | XML for Requirements Interchange Data |
| xrio | OMICRON Test Universe Extended RIO Object |
| xrk | AiM Tech EVO4S Logger Data |
| xrl | Concordance Markup Data |
| xrl | OSCAR Rules Data |
| xrl | Rapidform XOR 3D Scan CAD Data |
| xrl | Sybase PowerDesigner Report Language Data |
| xrm-ms | Windows Vista Activation Certificate |
| xrnt | Renoise DSP Device-chains Data |
| xrr | Chiron NRG Runtime Report 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 |
| xsd | MAPublisher Custom Coordinate System Data |
| xsdif | Altova DiffDog Schema Data |
