| .KAN | Open Source | Datatiedostot | Kwalitan Annotation | Kwalitan | Open Source |
| .KBD | Autodesk, Inc. | Asetustiedostot | 3ds Max Keyboard Shortcuts File | Janko's Keyboard Generator | Open Source |
| .KCD | Symantec Corporation | Datatiedostot | Rshiphop.kcd Malware | Kayak | Open Source |
| .KDB | Open Source | Tietokantatiedostot | KeePass Database File | KeePass Password Safe | Open Source |
| .KDBX | Dominik Reichl | Datatiedostot | KeePass Password Database | KeePass Password Safe | Open Source |
| .KDEVELOP | Free Software Foundation | Sovelluskehittäjän tiedostot | KDevelop Project Data File | KDevelop | Open Source |
| .KDEVPRJ | Free Software Foundation | Sovelluskehittäjän tiedostot | KDevelop Project File | KDevelop | Open Source |
| .KDS | Knyzhov Dmitry | Asetustiedostot | KD Player Skin File | gVim | Open Source |
| .KEA | Panasonic Corporation | Datatiedostot | Panasonic KTS File | KEALib software | Open Source |
| .KEYSTORE | Oracle Corporation | Koodatut tiedostot | Java Keystore File | KeyStore Explorer | Open Source |
| .KFI | Unknown Developer | 3D-kuvatiedostot | 3D Forgastest Editor Data | 3D Object Converter | Open Source |
| .KFX | Amazon | eBook Tiedostot | Amazon KF10 eBook File | Calibre | Open Source |
| .KGB | Open Source | Pakatut tiedostot | KGB Archive File | KGB Archiver | Open Source |
| .KHF | Open Source | Datatiedostot | Kwalitan Data File | Kwalitan | Open Source |
| .KHS | Open Source | Harvinaiset Tiedostot | Kwalitan History Data File | Kwalitan | Open Source |
| .KIWI | Open Source | Datatiedostot | KiwiViewer Scene | KiwiViewer | Open Source |
| .KIX | Ruud Van Velsen | Suoritettavat tiedostot | KiXtart Script File | PSPad | Open Source |
| .KMAP | Open Source | Harvinaiset Tiedostot | LyX Keymap | Lyx | Open Source |
| .KMD | Open Source | Suoritettavat tiedostot | ABSTAT For Windows Batch File | ABstat | Open Source |
| .KMF | Open Source | Datatiedostot | Kwalitan Memo File | Kwalitan | Open Source |
| .KML | Keyhole Corporation | GIS-tiedostot | Keyhole Markup Language File | Blender (With Google Earth Importer Plugin) | Open Source |
| .KMY | Open Source | Datatiedostot | KMyMoney Data File | KMyMoney | Open Source |
| .KMZ | Google | GIS-tiedostot | Google Earth Placemark File | Blender (With Google Earth Importer Plugin) | Open Source |
| .KO | Open Source | Järjestelmätiedostot | Linux Kernel Module File | Linux | Open Source |
| .KOC | Open Source | Datatiedostot | Koha Offline Circulation Data | Koha | Open Source |
| .KOR | Epic Games | Pelitiedostot | Unreal Engine Language Localization | PSPad | Open Source |
| .KPR | Open Source | Datatiedostot | KPresenter Presentation | KOffice | Open Source |
| .KPT | Open Source | Tekstitiedostot | KPresenter Template File | KOffice | Open Source |
| .KRA | Open Source | Graafiset Tiedostot | Krita Image | Krita | Open Source |
| .KRF | SPARTA, Inc. | Datatiedostot | DNSSEC-Tools Keyrec Data File | KMESS (Kevin's Mesh Efficiency Simulator Software) | Open Source |
| .KS | Debian | Järjestelmätiedostot | Kickstart File | KeyStore Explorer | Open Source |
| .KSG | Open Source | 3D-kuvatiedostot | Kwalitan Segment File | Kwalitan | Open Source |
| .KSH | AT&T Labs | Suoritettavat tiedostot | Unix Korn Shell Script | AbiWord | Open Source |
| .KSM | Pfaff | Datatiedostot | Pfaff Embroidery Design File Format | Embroidermodder 2 | Open Source |
| .KTE | Open Source | Datatiedostot | Kite Design File | FoilMaker | Open Source |
| .KTX | Open Source | Datatiedostot | Kwalitan Data File | Kwalitan | Open Source |
| .KU | Open Source | Datatiedostot | Knowledge Explorer Knowledge Representation Knowledge Unit | my Knowledge Explorer | Open Source |
| .KVA | Open Source | Pakatut tiedostot | KVIrc Compressed Archive | KVIrc | Open Source |
| .KVC | Open Source | Datatiedostot | KVC | KVIrc | Open Source |
| .KVS | Open Source | Sovelluskehittäjän tiedostot | KVIrc Script | KVIrc | Open Source |
| .KVT | Open Source | Asetustiedostot | KVIrc Heme | KVIrc | Open Source |
| .KWB | Open Source | Datatiedostot | Kwalitan Work File | Kwalitan | Open Source |
| .KWD | KDE | Tekstitiedostot | KWord Document | KOffice | Open Source |
| .KWT | Open Source | Asetustiedostot | KVIrc Theme | KVIrc | Open Source |
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