| f4 | Fortran IV Source Code |
| f77 | Fortran Source Code |
| f90 | Fortran Source Code |
| f95 | Fortran 95 Source Code |
| facefx | FaceFX Actor File |
| faces | FacesServlet Page |
| factor | Factor Source Code |
| fal | Falcon Script |
| fam | Falcon Compiled Module |
| fasl | Lisp Source Code |
| fb | Gforth Blocks File |
| fbap | FinalBuilder Action Package |
| fbl5 | FinalBuilder Project Log |
| fbl6 | FinalBuilder Project Log |
| fbp | wxFormBuilder Project |
| fbpinf | FinalBuilder Project Info |
| fbv | FinalBuilder Persistent Variables File |
| fcb | FAAST Builder File |
| fce | ForeUI Custom Element |
| fcl | ForeUI Custom Library |
| fclr | Flowgorithm Color Scheme Data |
| fcs | CC5X C Compiler Function Call Structure |
| fd | Fortran Declaration File |
| fda | FlashDevelop Argument File |
| fdb | FlashDevelop Binary File |
| fdl | FlashDevelop Layout File |
| fdm | FlashDevelop Macro |
| fdml | Filemaker Dynamic Markup Language Document |
| fdt | FlashDevelop Template |
| fdz | FlashDevelop Zip File |
| feature | SharePoint Feature Data |
| fev | FMOD Audio Events |
| fex | WebFOCUS Procedure File |
| ffe | Microsoft DirectInput Force Feedback Effect |
| fgd | Valve Hammer Forge Game Data |