| qsn | TapCIS QuickScan Data |
| qsr | CARE-S Water Quality Simulation Results Data |
| qst | Intuit Quicken v4 Data File |
| qst | KaleidaGraph Style |
| qstx | Quest III Quote File |
| qsty | KaleidaGraph Style |
| qsw | QuickShow Workspace Data |
| qsx | QuickSurf Data |
| qt2 | ViewChoice QT2 Data |
| qt3d | QT 3D Data |
| qtb | ExamView Question Bank Data |
| qtch | QuickTime Player Cache |
| qtf | Qtracker Filter |
| qtg | QTgrader Data |
| qth | WinOrbit Observer Database |
| qtindex | Adobe Premiere QuickTime Index |
| qtindex | Adobe Premiere QTIndex |
| qtm | Quanquest Quantum Element Definitions Data |
| qtmp | Qtracker Mapshot Pack |
| qtpp | Qtracker Update Data |
| qtr | Vectorworks v11 Workspace |
| qtsx | QuickTapSurvey Data |
| qtt | Qtracker Application Theme Data |
| qtx | QuaSZ Texture |
| qtx | QuickTime Extension |
| qtxs | QuickTime Data |
| qtxt | QuickShow Text Data |
| qu2 | GPS2WorldWind Data |
| quad | Geomview Quadrilaterals Data |
| qual | Quality Score File |
