| .F&F | Unknown Developer | Uncommon Files | Netmino File | Netmino | Unknown Developer |
| .F07 | Unknown Developer | Font Files | DOS 7-pixel Screen Font | Unknown Software | Unknown Developer |
| .F0A | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .F1C | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .F3 | Unknown Developer | Uncommon Files | FLASH BIOS File | Unknown Software | Unknown Developer |
| .F32 | FMJ-Software | Audio Files | Raw 32-Bit Audio File | Unknown Software | Unknown Developer |
| .F3LA | Corel | Graphic Files | Corel Texture File | Unknown Software | Unknown Developer |
| .FAC | Newera Software Technology, Inc. | Raster Image Files | FACE Graphic File | FromFace | Unknown Developer |
| .FACE | Newera Software Technology, Inc. | Raster Image Files | FACE Graphic File | FromFace | Unknown Developer |
| .FAFF | Unknown Developer | Spreadsheet Files | Professional Calc Spreadsheet File | Professional Calc | Unknown Developer |
| .FAST | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FBA | Unknown Developer | Uncommon Files | Mamew20 Data File | Mamew20 | Unknown Developer |
| .FC | OpenText | Settings Files | FirstClass Settings File | Unknown Software | Unknown Developer |
| .FCX | Patton & Patton Software | 3D Image Files | Flow Charting Diagram File | Unknown Software | Unknown Developer |
| .FDCSS | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FDV | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FEF | Unknown Developer | Uncommon Files | Steuer 2001 File | Steuer2001 | Unknown Developer |
| .FEL | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .FENDER | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FFR | Unknown Developer | Compressed Files | FFR Compressed Archive | Unknown Software | Unknown Developer |
| .FGX | Unknown Developer | Uncommon Files | Formula Graphics Project File | Formula Graphics | Unknown Developer |
| .FGZ | Unknown Developer | Compressed Files | Formula Graphics Standalone Presentation Archive | Formula Graphics | Unknown Developer |
| .FILE | Unknown Developer | Uncommon Files | Generic Windows File | Unknown Software | Unknown Developer |
| .FILELOCK | Unknown Developer | Encrypted Files | FileLock Data | Unknown Software | Unknown Developer |
| .FILES | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FILTER | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FIM | Terry W Gintz and Jules Ruis | Data Files | Fractal Imaginator Data Or Parameter | Unknown Software | Unknown Developer |
| .FINAL | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FIQ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FISH | Unknown Developer | Data Files | 3D Fish Tank File | Unknown Software | Unknown Developer |
| .FIX | Corey Zeke Womack (Torrunt) | Graphic Files | Vimage Image File | Unknown Software | Unknown Developer |
| .FIXED | Unknown Developer | Uncommon Files | DLLbackup Root File | Unknown Software | Unknown Developer |
| .FJO | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FLE | Unknown Developer | Settings Files | Scanner Settings File | Unknown Software | Unknown Developer |
| .FLETCH | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FLEX | Unknown Developer | Data Files | Flexi Data Smoothing File | Unknown Software | Unknown Developer |
| .FMC | Interscape | Data Files | FormConnect Form File | Unknown Software | Unknown Developer |
| .FN_ | Unknown Developer | CAD Files | CAD File | Unknown Software | Unknown Developer |
| .FONTS | Unknown Developer | Font Files | Font File | Unknown Software | Unknown Developer |
| .FORMATTER | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FORUM | Apple | Data Files | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .FR12 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FR6 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FRC | Dovetail Games | Game Files | FS Recorder File | FS Recorder | Unknown Developer |
| .FSE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FSF | Microsoft Corporation | Temporary Files | Microsoft Office Cache Data | Unknown Software | Unknown Developer |
| .FUQ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .FUZZY | Unknown Developer | Data Files | Fuzzy Logic File | Unknown Software | Unknown Developer |
| .FVP | Unknown Developer | Settings Files | File Viewer Plus Batch Presets File | Unknown Software | Unknown Developer |
| .FVT | Fast Search & Transfer ASA | Video Files | FAST Search & Transfer Video File | Unknown Software | Unknown Developer |
| .FWA | Piotr Fusik | Raster Image Files | Fun With Art Picture Image | Mamew20 | Unknown Developer |
| .FWF | Unknown Developer | Data Files | Xwave FWF Data | Unknown Software | Unknown Developer |
| .FXM | pmG Worldwide | 3D Image Files | MessiahStudio Motion File | RdosPlay | Unknown Developer |
| .FY | Unknown Developer | Font Files | Fontasy Publisher Font | Fontasy Publisher | Unknown Developer |
| .FYB | Unknown Developer | Uncommon Files | Bold Font File | Fontasy Publisher | Unknown Developer |
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