| pyx | Pyrex Source |
| q | QL-R-kemi Unformatted Source |
| qbe | dBASE IV Saved Query |
| qbs | QuickBasic Source Code |
| qc | QuakeC Source Code |
| qcf | QuickBasic Coordinates File |
| qf | Qompose Web Page Template |
| qhc | QT Help Collection |
| qip | Altera Quartus II IP File |
| qlb | QuickBASIC Library |
| qlf | SWI-Prolog Quick Load File |
| qlp | Yasol QLP Program |
| qm | Qt Compiled Translation Source |
| qml | QML Source Code |
| qmlc | QQmlEngine QML Cache |
| qmm | QM Compiled Macro |
| qpg | QNX Package Generation File |
| qpm | QNX Package Manifest File |
| qpr | QNX Package Repository File |
| qpr | Visual FoxPro Query Program |
| qps | CUTEr QPS Model |
| qpx | Visual FoxPro Compiled Query Program |
| qrc | QT Resource Collection File |
| qrp | QuickReport Data |
| qs | QL-R-kemi Styled Source |
| qsl | Qedit Script |
| qss | QT Style Sheet |
| qtd | Qt Creator Trace Data |
| qvs | QlikView Script |
| qx | Quex Input File |
| qx | Quexal Source Code |
| qxm | Quexal Macro File |
| r | R Source Code |
| r | REBOL Source Code |
| r | Pegasus Mail Resource File |