| Extension | File Type | Files scanned | Contributor |
| Q | Quantum compressed archive | 5 | |
| Q3O | Quick3D Model | 41 | |
| QAT | Office Quick Access Toolbar info | 5 | |
| QBB | Intuit QuickBooks Backup | 6 | |
| QBW | Intuit QuickBooks for Windows | 8 | |
| QCF | Quickbasic Coordinates File | 2 | |
| QCP | QualComm PureVoice | 18 | |
| QDF | Quicken data | 3 | |
| QFC | QuickFileCollection archive | 3 | |
| QFX | Quick Link II Fax bitmap | 3 | |
| QFX | Quicken Transfer file | 7 | |
| QIC | Windows 98 MSBackup backup set | 5 | |
| QIF | Quicken Interchange Format | 9 | |
| QLB | Microsoft Basic 7.x Quick library | 72 | |
| QLI | Statler Stitcher | 6 | |
| QM | Qt Message file | 51 | |
| QP03 | qpress compressed archive | 18 | Label |
| QPW | Quattro Pro for Windows spreadsheet | 21 | |
| QRP | QuickReport Report | 8 | |
| QRS | SlickRun MagicWord Pack | 6 | |
| QSD | Quicken Win Data | 13 | |
| QSF | Quintessential Player Family Skin | 16 | |
| QSK | Quintessential Player Kid Skin | 10 | |
| QST | Zelda Classic Quest | 2 | |
| QSU | Zelda Classic Quest (Unencoded) | 2 | |
| QTCH | Quicktime Cached data | 4 | |
| QTL | QuickTime Media Link | 6 | |
| QTP | QuickTime Preferences | 7 | |
| QTZ | Quartz Composer data | 20 | |
| QUERY | Microsoft PCHealth query | 6 | |
| QVW | QlikView document | 50 | roentgen |
| QWK | QWK offline mail packet (ZIP compressed) | 13 | |
| QX | Quexal sourcecode | 9 | |
| QXD | Quark XPress document | 143 | Thomas Werner |
| QXM | Quexal macro | 12 | |
| QXP | QuarkXpress project | 3 | |
| QZ | Create A Quiz file | 2 | |
| QZD/QZE/QZS | QuizPro quiz data | 9 | |
