| File Extension | Description |
| F | Archive |
| F | Fortran language source code file (in fixed form) |
| F01 | Fax |
| F03 | Fortran language source code file (in free form) |
| F2R | Farandole Linear Module |
| F3R | Farandole Blocked Linear Module |
| F4 | Fortran IV source code file |
| F4A | Audio for Adobe Flash Player |
| F4B | Audio Book for Adobe Flash Player |
| F4P | Protected Video for Adobe Flash Player |
| F4V | Video for Adobe Flash Player |
| F77 | Fortran language source code file (in fixed form) |
| F90 | Fortran language source code file (in free form) |
| F95 | Fortran language source code file (in free form) |
| F96 | Fax |
| FAC | see FACE |
| FACE | Usenix FACE graphics file |
| FAM | Famtasia Famicom image format |
| FAQ | Frequently Asked Questions text file |
| FAR | Music format (Farandole Composer Module) |
| FAS | Macsyma compiled program |
| FAX | Fax (raster graphics in CCITT format) |
| FBM | Fuzzy Bitmap |
| FC | Spell checking dictionary |
| FCM | Binary file patch file (forward compression) |
| FD | Declaration file |
| FD | Field offsets for compiler |
| FD | Front Door' resource files |
| FDB | Font Definition Block |
| FDS | fwNES Famicom Disk System image |
| FDS | Headerless Famicom Disk System image |
| FDW | Form |
| FE | Data |
| FEB | Button bar for Figure Editor |
| FEI | Fatal Error Infotable |
| FES | File produced when a fileless occurrence in 3D Topicscape is exported to Windows |
| FF | Intelligont FIAS format |
| FF | Outline font description |
| FFE | Front Fareast Famicom image format |
| FFF | Fax |
| FFI | Atech FastFont (AllType) |
| FFIVW | File Format for the Interchange of Virtual Worlds |
| FFT | Dca/FFT Final Form Text text file (DisplayWrite) |
| FFT | DCA/FFT Final Form Text text file |
| FH3 | Vector graphics |
| FH4 | Vector graphics |
| FI | Interface file |
| FIF | Fractal Image Format file |
| FIG | Figure File |
| FIL | Table Data |
| FIL | File template |
| FIL | Filelist |
| FIL | Files list object file |
| FIL | Mirror. FIL is the name given to the saved FAT by the mirror program included in some versions of DOS and in PCTools |
| FIL | Overlay |
| FIL | File which was moved to the Virus Vault by AVG |
| FILM | Filmkey film file |
| FIN | Print-formatted text file |
| FIO | Aldus PhotoStyler graphics filter |
| FIO | Image PALS viewer DLL |
| FIT | File Index Table |
| FIT | see FITS |
| FITS | Flexible Image Transport System |
| FIX | Patch file |
| FKY | Macro file |
| FLA | Adobe Flash files' basic format |
| FLAC | Audio codec, Audio file format |
| FLAME | Fractal configuration file |
| FLB | Format library |
| FLC | Animation format FLIC >320x200 |
| FLD | Folder |
| FLI | Animation format FLIC 320x200 |
| FLI | TeX font library |
| FLM | Film Roll |
| FLP | Flstudio project file |
| FLT | Data/file conversion filter (or overlay) |
| FLT | Filter file |
| FLT | MultiGen Flight |
| FLT | Support file - graphics filter |
| FLV | Flash video file |
| FLX | Animation format |
| FLX | Compiled binary |
| FM | Database |
| FM1 | Spreadsheet format overlay |
| FM3 | Device driver |
| FM3 | Spreadsheet |
| FMB | File Manager Button bar |
| FMF | Font or icon file |
| FMK | Makefile |
| FMO | Compiled format file |
| FMT | Format file |
| FMT | Gate3 format file |
| FMT | Style sheet |
| FMV | Full Motion Video file |
| FN3 | Font file |
| FND | Files searching properties |
| FNI | FileNet Native Document |
| FNK | FunkTracker music module |
| FNM | Fannie Mae Residential Loan Data (RLD) format for mortgage submission to DO/DU. |
| Fnn | DOS screen text font - height nn pixels |
| FNT | Font file |
| FNX | Inactive font |
| FO1 | Font file |
| FO2 | Font file |
| FOG | Fontographer Database File |
| FOL | Folder of saved messages |
| FON | Log of all calls |
| FON | Terminate phonebook |
| FON | Windows bitmapped font file |
| FONT | Font data |
| FOP | Freedom of the Press graphic file |
| FOR | Form |
| FOR | Fortran language source file |
| FOT | Installed Truetype font |
| FOX | Foxbase executable (precompiled .prg) |
| FP | Final Page file |
| FP | Tiff file |
| FP | Video file |
| FP3 | Database |
| FP4 | Database |
| FP5 | Database |
| FP7 | Database |
| FPC | Catalog |
| FPD | TMT Pascal compiled unit |
| FPM | Configuration file |
| FPT | Foxpro memo field tables |
| FPU | Configuration file |
| FPW | Floorplan drawing |
| FPW | Configuration file |
| FPX | FlashPix Bitmap Image File |
| FR3 | Renamed dBASE III+ form file |
| FRF | FontMonger Database file |
| FRG | Uncompiled report file |
| FRL | GP-Forth library |
| FRM | Registration or other form |
| FRM | Report file |
| FRM | Visual Basic Form |
| FRO | Compiled report file |
| FRP | Form |
| FRS | Screen Font Resource |
| FRT | Additional (FPT) report description file |
| FRT | GP-Forth source file |
| FRX | Main (DBF) report description file |
| FRX | Visual Basic binary program file |
| FSA | Applied Biosystems Genetic Analysis data file |
| FSIM | Simulation File Format |
| FSL | Form |
| FSM | Farandole Composer WaveSample |
| FSPROJ | Habanero Firestarter project |
| FST | Linkable program |
| FST | Temporal database file |
| FSTICK | Temporal database file |
| FSX | Data |
| FTM | Fielded Text Meta - Contains schema/Meta for a Fielded Text file |
| FTM | Font file |
| FTP | Configuration |
| FTX | Declared Fielded Text |
| FTXT | text |
| FW | Database |
| FW2 | Database |
| FW3 | Database |
| FWEB | Fortran WEB |
| FX | On-line guide |
| FXD | Phonebook |
| FXP | Foxpro executable (precompiled .prg) |
| FXS | FAX Transmit Format graphics file |
| FYF | FileLoc |
