| fmdl | Konami Fox Engine Model |
| fmg | Harbour MiniGUI IDE Form |
| fmo | dBASE IV Compiled Object |
| fmt | Oracle Forms Form Module Text |
| fmx | Oracle Forms Form Module Executable |
| fn | GCL Cross Referencing Data |
| fo1 | Borland Turbo C Font Data |
| fo2 | Borland Turbo C Font Data |
| fon | Hitachi Ladder Editor Force File |
| footer | WebSTAR Directory Indexer Footer |
| for | Fortran Source Code |
| form | Gambas V2 Form |
| forth | Forth Source Code |
| fox | FoxBase Compiled Executable |
| fpa | Front Panel Express Order Data |
| fpd | Front Panel Express Design |
| fpp | Fortran Source Code |
| fpq | Microsoft Visual FoxPro Updatable Query File |
| fprg | Flowgorithm Program |
| fps | FPS Creator Segment |
| fpt | Visual FoxPro Memo |
| fr3 | FastReport v3 Form |
| frf | FreeReport Form |
| frg | DBase IV Uncompiled Report |
| frm | Visual Basic Form |
| frt | Visual FoxPro Report Memo |
| frt | Forth Source Code |
| frx | Visual FoxPro Report |
| fs | F# Implementation |
| fs | Forth Source Code |
| fsb | Form Z Compiled Script |
| fscr | ChromeEd Forester Data Script |
| fsi | F# Signature File |
| fsl | Form Z Script |
| fsq | CryENGINE Facial Editor Sequence |