| fmsh | Autodesk Inventor Mesh Data |
| fmt | GAUSS Engine Matrix Data |
| fmtr | FileMaker Pro Transfer Data |
| fmu | Functional Mock-up Unit Data |
| fmv | FME Desktop Viewspace Data |
| fmw | FME Workbench |
| fmwt | FME Desktop Workbench Template |
| fmx | FME Desktop Custom Transformers Data |
| fmxlist | FME Desktop User-defined Transformer List |
| fn | STK Facility Networks File |
| fna | FASTA Sequence |
| fnbk | Food Network Recipe Manager Data |
| fnc | Frogans Player Network Certificate |
| fnet | FileMaker Pro Network Data |
| fng | Font Navigator Group Data |
| fnl | EES File Names List |
| fnm | Lucene Field Name Data |
| fnm | SOBEK Filenames Data |
| fno | Folio Infobase Data |
| fnrecipes | Food Network Recipe Manager Data |
| fnsp | Apple FontSync Script |
| fnw | FLARENET Model Data |
| fnx | Fenix Key Data |
| fo | 602XML Form Filler Data |
| fob | Microsoft Dynamics NAV Object Container |
| foc | FOCUS Database |
| fod | EZ-Forms Form Relationship Data |
| fof | EZ-Forms Filled Out Form |
| fog4 | Fontographer v4 Data |
| fol | PFS First Choice Database |
| folder | Windows Explorer Folder Data |
| foli | Foliaro Data |
| fom | EZ-Forms Fill Out Master Form |
| fop | InfoZoom Protected Data |
| fot | InfoZoom Template |