| k9 | DataFlex Index |
| ka | Karma Assets Data |
| kab | Kmail Addressbook Data |
| kad | NI Kore Data |
| kahl | THINK Pascal KAHL Text |
| kal | Hondata KManager Calibration Data |
| kali | Kali Linux Related Data |
| kam | BEL Framework KAM Database |
| kan | Kwalitan Annotation Data |
| kbb | Jetico BestCrypt Key Block Backup |
| kbd | MountFocus Keyboard Designer Keyboard |
| kbf | MyInfo Document |
| kbi | Keirsey Bates Temperament Sorter Index |
| kbk | Medeco XT Codebooks for Keys Data |
| kbp | Keirsey-Bates Temperament Sorter Profile Data |
| kbs | Keyboard Script |
| kburl | Knowledge Master URL Data |
| kbx | GnuPG Keybox File |
| kcc | KeywordConvert Combined List |
| kcd | Kayak Network Definitions Data |
| kcl | KeywordConvert List |
| kcm | KonyvCalc Data |
| kco | Kwalitan Codes Data |
| kcs | Keep and Share Offline Calendar Data |
| kct | Kwalitan Categories Data |
| kct | Knit Visualizer 1.0 Chart |
| kd3 | Yayoi Kaikei Accounting Data |
| kdb | KeePass v1 Password Database |
| kdbp | KeePass Fast KDBP Data |
| kdbx | KeePass v2 Password Database |
| kdd | Adobe Authorware Knowledge Display Data |
| kdi | KD Player Skin Image |
| kdl | Kill The Deadline Data File |
| kdo | Kudo Image Browser Data |
| kdr | Kinetica Data File |