| kct | Kwalitan Categories Data |
| 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 |
| kds | KD Player Skin |
| kdt | Medbasin Evaporation Data |
| kdx | Google Earth Import Definition |
| kdz | Kaspersky Anti-virus Database |
| ked | KEDIT Macro File |
| ked | KEDIT Macro Library |
| keepsafe | KeepSafe Folder |
| kef | KAPA mpi Exported Data |
| keg | Kieler Editor for Graphs Model |
| kegdi | Kieler Editor for Graphs GMF Notation Model |
| kek | IBM Personal Communications KEK Storage |
| ken | Player Cdcheck Compressed Data |
| ket | Kermeta Emitter Template |
| kex | KEDIT Macro File |
| kexi | Kexi Database |
| kexic | Kexi Database Connection Data |
| kexis | Kexi Database Shortcut |
| key | Tinker Keyword Parameters |
| key | SmartWare Database Key File |
| key | KetuFile Encryption Key Data |
| keychain | Mac OS X Keychain |
| keyhelp | Zoom Player Keyboard Macros Data |
| keylist | Zoom Player Virtual Keyboard Layout |
| keyring | Java Key Store |
| keystore | Java Key Store |