| failed | IBM Content Navigator Failed Task Log |
| fak | HP MPE/iX Fixed ASCII KSAM Data |
| fam | PLINK Individual Information File |
| fan | Form Z Animation |
| fap | Oracle Documaker Sections Data |
| fap | Visage Mpeg-4 ASCII Facial Animation Parameters File |
| faqt | FAQTool Data |
| fasta | FASTA Sequence |
| fastq | FASTQ Sequence |
| fat | Zinf Theme |
| fau | Creator Collapsed Fault List |
| fav | Microsoft Outlook Navigation Bar |
| favorite | Apple iDVD Favorites Data |
| favs | PlasmaEPG Saved Favorites Data |
| faz | DeskMate Generic Character Data |
| fb! | FlashGet Unfinished File |
| fb1 | FAWAVE Data File |
| fba | FinalBurn Alpha Image |
| fbat | FAR HTML Batch Compile Data |
| fbc | Family Tree Maker Compressed Backup Data |
| fbexplore | FileBoss Explorer Data |
| fbk | Microsoft Dynamics NAV Database Backup |
| fbk | Family Tree Maker Backup Data |
| fbl | iGO Map file |
| fbmod | Frosty Tool Suite Data |
| fbn | Sony-Ericsson Phone Flash Filesystem |
| fbr | BrainVoyager QX Fiber Coordinates Data |
| fbv | GrafNav Exported Binary Values Data |
| fbwinsx | FileBoss Internal Data |
| fc1 | FCEUX Saved State |
| fc2 | FCEUX Saved State |
| fc2 | Poser Face Data |
| fc3 | FCEUX Saved State |
| fca | Omnis Web Client Form Cache |
| fcat | Fact200 Categories Data |