| .K02 | SoftVelocity | Pliki z danymi | Clarion Data File | Clarion | SoftVelocity |
| .K2 | Data Access Worldwide | Pliki z danymi | DataFlex Index | DataFlex | Data Access Worldwide |
| .K4 | Data Access Worldwide | Pliki z danymi | DataFlex Index | DataFlex | Data Access Worldwide |
| .K7 | Data Access Worldwide | Pliki z danymi | DataFlex Index | DataFlex | Data Access Worldwide |
| .KAD | Native Instruments | Pliki z danymi | Kore User Data | Kore | Native Instruments |
| .KAL | Kratos Analytical | Pliki z danymi | Kratos Vision Data File | CasaXPS | Casa Software Ltd |
| .KAN | Open Source | Pliki z danymi | Kwalitan Annotation | Kwalitan | Open Source |
| .KAP | Maptech | Pliki z danymi | BSB Chart Image File | Maptech U.S. Boating Charts | Maptech |
| .KAS | Evil Laboratories | Pliki z danymi | Karaoke File | EvilLyrics | Evil Laboratories |
| .KBD | Autodesk, Inc. | Pliki z danymi | 3ds Max Keyboard Shortcuts File | Autodesk 3ds Max | Autodesk, Inc. |
| .KBF | Milenix Software Ltd. | Pliki z danymi | MyInfo Document | MyInfo | Milenix Software Ltd. |
| .KBI | Derek Hendrikz | Pliki z danymi | Keirsey-Bates Temperament Sorter Index | Keirsey-Bates Temperament Sorter | Keirsey Group |
| .KBK | Unknown Developer | Pliki z danymi | Medeco XT Codebooks For Keys Data | Unknown Software | Unknown Developer |
| .KBN | TeamSpeak Systems | Pliki z danymi | TeamSpeak Keybinding File | TeamSpeak | TeamSpeak Systems |
| .KBR | Unknown Developer | Pliki z danymi | Keirsey-Bates Temperament Sorter Data | Unknown Software | Unknown Developer |
| .KBS | PC Dirck | Pliki z danymi | Keyboard Script File | PC Dirck Keyboard Script | PC Dirck |
| .KBX | GNU Project | Pliki z danymi | GNU Privacy Guard Keybox File | GNU Privacy Guard | GNU Project |
| .KCD | Symantec Corporation | Pliki z danymi | Rshiphop.kcd Malware | Avira Antivirus Pro 2016 | Avira Operations GmbH & Co. KG. |
| .KCL | Nintendo | Pliki z danymi | Mario Kart Collision File | Mario Kart Wii | Nintendo |
| .KCM | MM. Sys Bt. | Pliki z danymi | KönyvCalc File | KönyvCalc | MM. Sys Bt. |
| .KCX | Kea Software | Pliki z danymi | Kea Coloring File | Kea Coloring Book | Kea Software |
| .KD3 | Yayoi Co., Ltd. | Pliki z danymi | Yayoi Kaikei Accounting Data | Yayoi Accounting | Yayoi Co., Ltd. |
| .KDBX | Dominik Reichl | Pliki z danymi | KeePass Password Database | KeePass Password Safe | Open Source |
| .KDC | Kaspersky Lab | Pliki z danymi | Kaspersky Virus Database File | Kaspersky Anti-Virus | Kaspersky Lab |
| .KDF | Kinko's | Pliki z danymi | Kinko's File Prep Tool Data | Kinko's File Prep Tool | Kinko's |
| .KDS | Knyzhov Dmitry | Pliki z danymi | KD Player Skin File | Microsoft Notepad | Microsoft Corporation |
| .KDT | National Technical University of Athens | Pliki z danymi | Medbasin Evaporation Data | Medbasin | National Technical University of Athens |
| .KDZ | Kaspersky Lab | Pliki z danymi | Kaspersky Virus Bases File | Kaspersky Anti-Virus | Kaspersky Lab |
| .KEA | Panasonic Corporation | Pliki z danymi | Panasonic KTS File | Panasonic HD Writer AE | Panasonic Corporation |
| .KERNEL | Apple | Pliki z danymi | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .KEY | Unknown Developer | Pliki z danymi | License/ Encrypted Security Key File | Avira Antivirus Pro 2016 | Avira Operations GmbH & Co. KG. |
| .KEYNOTE | Apple | Pliki z danymi | iWork Keynote '06 Presentation | Apple Keynote | Apple |
| .KHF | Open Source | Pliki z danymi | Kwalitan Data File | Kwalitan | Open Source |
| .KID | Inspiration Software Inc. | Pliki z danymi | Kidspiration Document | Kidspiration | Inspiration Software Inc. |
| .KIF | Autodesk, Inc. | Pliki z danymi | AutoCAD Key Index File Format | Autodesk AutoCAD | Autodesk, Inc. |
| .KIK | Apple | Pliki z danymi | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .KIWI | Open Source | Pliki z danymi | KiwiViewer Scene | KiwiViewer | Open Source |
| .KJV | Costas stergiou | Pliki z danymi | TheWord Data | theWord | Costas stergiou |
| .KK2 | Payroll Associates, LLC | Pliki z danymi | ViewChoice | PayChoice | Payroll Associates, LLC |
| .KKT | TTS | Pliki z danymi | TTS-Kone File | TTS-Kone | TTS |
| .KKW | Adobe Systems Incorporated | Pliki z danymi | Adobe RoboHelp Keyword Help Project Index File | Adobe RoboHelp | Adobe Systems Incorporated |
| .KLA | Unknown Developer | Pliki z danymi | KLARFF Map Data | Unknown Software | Unknown Developer |
| .KLB | Software MacKiev | Pliki z danymi | KidPix Sticker, Stamp Album | Kid Pix | Software MacKiev |
| .KLF | Frank Böpple | Pliki z danymi | KaloMa Data | KaloMa | Frank Böpple |
| .KLG | Unknown Developer | Pliki z danymi | KOFIA Log | KOFIA | Unknown Developer |
| .KLI | Unknown Developer | Pliki z danymi | KalKulator Linear Algebra Data | Unknown Software | Unknown Developer |
| .KLIP | Klipfolio Inc. | Pliki z danymi | KlipFolio Klip | KlipFolio | Klipfolio Inc. |
| .KLK | Orgadata AG | Pliki z danymi | Orgadata LogiKal Data | LogiKal | Orgadata AG |
| .KLP | Phoenix Contact | Pliki z danymi | CLIP PROJECT Terminal-Strip Project | Clip Project | Phoenix Contact |
| .KLX | Sinasoft Co. | Pliki z danymi | Kelk 2000 Data | Kelk 2000 | Sinasoft Co. |
| .KM | BMC | Pliki z danymi | BMC Patrol Knowledge Module | BMC | BMC |
| .KM2 | KAISHA-Tec | Pliki z danymi | ActiveModeler Process Map | Avantage | KAISHA-Tec |
| .KMA | Correlate | Pliki z danymi | Correlate Archive File | Correlate | Correlate Client |
| .KMD | Open Source | Pliki z danymi | ABSTAT For Windows Batch File | ABstat | Open Source |
| .KMF | Open Source | Pliki z danymi | Kwalitan Memo File | Kwalitan | Open Source |
| .KMO | Unknown Developer | Pliki z danymi | Commercial Bank Czech Financial Data Exchange Format | Unknown Software | Unknown Developer |
| .KMS | Correlate | Pliki z danymi | Correlate Solutions File | Correlate | Correlate Client |
| .KMY | Open Source | Pliki z danymi | KMyMoney Data File | KMyMoney | Open Source |
| .KMZ | Google | Pliki z danymi | Google Earth Placemark File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .KNB | Unknown Developer | Pliki z danymi | Neuro-Expert System Knowledge Base Data File | Neuro-Expert System | Unknown Developer |
| .KND | NEPLAN AG | Pliki z danymi | NEPLAN-DOS Import Or Export File | NEPLAN Electricity | NEPLAN AG |
| .KNF | Orchida Soft | Pliki z danymi | Orchida Knitting System Data | Orchida Knitting System | Orchida Soft |
| .KNO | EvREsearch LTD. | Pliki z danymi | DigIN Serialized Break Model | DigIN | EvREsearch LTD. |
| .KOC | Open Source | Pliki z danymi | Koha Offline Circulation Data | Koha | Open Source |
| .KOK | Recisio | Pliki z danymi | KaraFun Karaoke Data | KaraFun | Recisio |
| .KOS | South-Western Educational Publishing | Pliki z danymi | MicroType Pro Document File | MicroType Pro | South-Western Educational Publishing |
| .KPF | ActiveState | Pliki z danymi | Komodo Project File | ActiveState Komodo IDE | ActiveState |
| .KPP | Software MacKiev | Pliki z danymi | Kid Pix Presentation | Kid Pix | Software MacKiev |
| .KPR | Open Source | Pliki z danymi | KPresenter Presentation | KOffice | Open Source |
| .KPX | Software MacKiev | Pliki z danymi | Kid Pix Picture | Kid Pix | Software MacKiev |
| .KRB | SourceForge | Pliki z danymi | Pyke Knowledge Rule Base | Pyke | SourceForge |
| .KRC | Kra-Tronic Corporation | Pliki z danymi | Mouse And Key Recorder Macro File | Kra-Tronic Corporation Mouse and Key Recorder | Kra-Tronic Corporation |
| .KRF | SPARTA, Inc. | Pliki z danymi | DNSSEC-Tools Keyrec Data File | DNSSEC-Tools | SPARTA, Inc. |
| .KSA | Kubotek Corporation | Pliki z danymi | KeyCreator Settings Archive File | Kubotek USA KeyCreator | Kubotek Corporation |
| .KSM | Pfaff | Pliki z danymi | Pfaff Embroidery Design File Format | Embroidermodder 2 | Open Source |
| .KSP | Luxion | Pliki z danymi | Keyshot Package | Keyshot | Luxion |
| .KSW | Cosmic Patterns Software | Pliki z danymi | Kepler Workflow Document | Kepler | Cosmic Patterns Software |
| .KTE | Open Source | Pliki z danymi | Kite Design File | FoilMaker | Open Source |
| .KTH | Apple | Pliki z danymi | iWork Keynote Theme | Apple Keynote | Apple |
| .KTI | Kelvin TOP-SET | Pliki z danymi | Kelvin TOP-SET Investigator Data | Kelvin TOP-SET Investigator | Kelvin TOP-SET |
| .KTX | Open Source | Pliki z danymi | Kwalitan Data File | Kwalitan | Open Source |
| .KU | Open Source | Pliki z danymi | Knowledge Explorer Knowledge Representation Knowledge Unit | my Knowledge Explorer | Open Source |
| .KUF | K.Y.N.G | Pliki z danymi | K.Y.N.G Update Data | K.Y.N.G | K.Y.N.G |
| .KUU | K.Y.N.G | Pliki z danymi | K.Y.N.G Data File | K.Y.N.G | K.Y.N.G |
| .KVB | MSR Enterprises | Pliki z danymi | Klick-N-View Business Cards | Klick-N-View Business Cards | MSR Enterprises |
| .KVC | Open Source | Pliki z danymi | KVC | KVIrc | Open Source |
| .KW3 | Pacific Software Publishing, Inc. | Pliki z danymi | KanjiWORD Document File | KanjiWORD | Pacific Software Publishing, Inc. |
| .KWB | Open Source | Pliki z danymi | Kwalitan Work File | Kwalitan | Open Source |
| .KWL | KDE | Pliki z danymi | KWalletManager File | KWalletManager | KDE |
| .KWO | KeyWallet GbR | Pliki z danymi | KeyWallet Encrypted Password Storage | KeyWallet | KeyWallet GbR |
| .KWZ | Nintendo | Pliki z danymi | Flipnote Studio 3D Flipnote Data | Flipnote Studio 3D | Nintendo |
| .KXP | SoftKey | Pliki z danymi | KEY Home Gourmet Data | KEY Home Gourmet | SoftKey |
| .KY | Sage | Pliki z danymi | Peachtext List Manager File | Peachtext | Sage |
| .KYN | ESTsoft | Pliki z danymi | ALSee Thumbnail Cache | ALSee | ESTsoft |
| .KZB | Rightware | Pliki z danymi | Kanzi Studio Binary Data | Kanzi Studio | Rightware |
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