| fcz | Poser Compressed Face Data |
| fd | STK Facility Database Main File |
| fdat | Fiasco Database Data File |
| fdata | NONMEM Data |
| fdc | Autodesk AutoCAD Fields Description |
| fde | AFP Form Definition |
| fdf | Origin Fitting Function Definition File |
| fdf | Format Description File |
| fdff | Fast Duplicate File Finder Data |
| fdk | Fluentizer Dictionary Data |
| fdm | SIPINA FDM Data |
| fdn | MODFLOW Drawdown Data |
| fdo | ModelSim Script |
| fdp | Viamichelin Map File |
| fdp | Epson PhotoQuicker Frame |
| fdt | Visilogic Utilities Full Data Table |
| fdt | Lucene Field Data |
| fdx | Lucene Field Index |
| fdx | Food Data Exchange File |
| fdxsl2 | FeedDemon Newspaper Style |
| fdxsl4 | FeedDemon Newspaper Style |
| fe | Surface Evolver Data File |
| feb | Sybase PowerDesigner Free Model Backup |
| fee | Precision Fees Data |
| feed | JRiver Media Center Feed Data |
| feed-ms | Microsoft RSS Feed Store |
| fef | Steuer 2001 FEF Data |
| fel | Fugawi Elevation Library Data |
| fem | Algor Simulation FEA Model |
| fem | Sesam GeniE FEM Data |
| fem | Sybase PowerDesigner Free Model |
| fen | Forsyth–Edwards Notation Data |
| fes | Topicscape Fileless Link Export |
| fet | FET Data |
| ffa | Microsoft Find Fast Status File |