| fsk | Atari 8-bit Tape Data |
| fsm | Splitty Master Split Data |
| fso | Adobe Flash Media Server Remote Shared Object |
| fsp | iGO Primo Map File |
| fsqueue | FeedStation Queue Data |
| fsrc | Fact200 Source Code |
| fss | Splitty Data Split |
| fssx | FolderSizes Snapshot Data |
| fst | GAUSS Engine String Data |
| fst | FAST Input Data |
| fst | PLINK Fixation Index Report |
| fstat | SAM Fragfinder Scoring Data |
| fsthumb | Wondershare Filmora Thumbnail Cache |
| fsz | Fractal Zplot Data |
| ft | EdgeCAM Feature Template |
| fta | OpenFTA File |
| ftbl | PIPE-FLO Fluid Data Table |
| ftch | Extensis Portfolio Image Database |
| ftes | Autodesk Inventor Stress Analysis Test Data |
| ftf | Xperia X10 Phone FTF Firmware |
| fth | FileMaker Pro Theme |
| ftmb | Family Tree Maker Backup Data |
| ftploc | Mac OS X Finder FTP Location Data |
| ftpquota | Pure-FTPd Quota Data |
| ftr | CONDOR Flight Track |
| ftv | CleverPath Forest and Trees View File |
| ftw | FontTwister Saved Text Effect |
| fuc | Frequently Used Commands |
| fud | FairUse Wizard Data File |
| ful | Microsoft Backup File List |
| furl | Fact200 Main Index Data |
| fus | FXpansion Uninstall Script |
| futr | NetIQ Identity Manager Future-dated Infotype Cache |
| fv | Fresh View Thumbnail Cache |
| fvb | TAC Vista Database Backup |