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