| k2 | DataFlex Index |
| k2p | Kryptel Encrypted Data |
| k3 | DataFlex Index |
| k4 | DataFlex Index |
| k5 | DataFlex Index |
| k6 | DataFlex Index |
| k7 | DCMO6 Emulator Tape Image |
| k7 | DataFlex Index |
| ka | Karma Assets Data |
| kab | Kmail Addressbook Data |
| kad | NI Kore Data |
| kadf | KetabeAvval Data Format File |
| kal | Hondata KManager Calibration Data |
| kam | BEL Framework KAM Database |
| kbb | Jetico BestCrypt Key Block Backup |
| kbd | MountFocus Keyboard Designer Keyboard |
| kbs | Keyboard Script |
| kbx | GnuPG Keybox File |
| kcd | Kayak Network Definitions Data |
| kcm | KonyvCalc File |
| kcs | Keep and Share Offline Calendar Data |
| kct | Knit Visualizer 1.0 Chart |
| kdb | KeePass v1 Password Database |
| kdbx | KeePass v2 Password Database |
| kdd | Adobe Authorware Knowledge Display Data |
| kdl | Kill The Deadline Data File |
| kdr | Kinetica Data File |
| kds | KD Player Skin |
| kdt | Medbasin Evaporation Data |
| kdx | Google Earth Import Definition |
