| .KMF | Open Source | Arquivos de dados | Kwalitan Memo File | Kwalitan | Open Source |
| .KMO | Unknown Developer | Arquivos de dados | Commercial Bank Czech Financial Data Exchange Format | Unknown Software | Unknown Developer |
| .KMS | Correlate | Arquivos de dados | Correlate Solutions File | Correlate | Correlate Client |
| .KMY | Open Source | Arquivos de dados | KMyMoney Data File | KMyMoney | Open Source |
| .KMZ | Google | Arquivos de dados | Google Earth Placemark File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .KNB | Unknown Developer | Arquivos de dados | Neuro-Expert System Knowledge Base Data File | Neuro-Expert System | Unknown Developer |
| .KND | NEPLAN AG | Arquivos de dados | NEPLAN-DOS Import Or Export File | NEPLAN Electricity | NEPLAN AG |
| .KNF | Orchida Soft | Arquivos de dados | Orchida Knitting System Data | Orchida Knitting System | Orchida Soft |
| .KNO | EvREsearch LTD. | Arquivos de dados | DigIN Serialized Break Model | DigIN | EvREsearch LTD. |
| .KOC | Open Source | Arquivos de dados | Koha Offline Circulation Data | Koha | Open Source |
| .KOK | Recisio | Arquivos de dados | KaraFun Karaoke Data | KaraFun | Recisio |
| .KOS | South-Western Educational Publishing | Arquivos de dados | MicroType Pro Document File | MicroType Pro | South-Western Educational Publishing |
| .KPF | ActiveState | Arquivos de dados | Komodo Project File | ActiveState Komodo IDE | ActiveState |
| .KPP | Software MacKiev | Arquivos de dados | Kid Pix Presentation | Kid Pix | Software MacKiev |
| .KPR | Open Source | Arquivos de dados | KPresenter Presentation | KOffice | Open Source |
| .KPX | Software MacKiev | Arquivos de dados | Kid Pix Picture | Kid Pix | Software MacKiev |
| .KRB | SourceForge | Arquivos de dados | Pyke Knowledge Rule Base | Pyke | SourceForge |
| .KRC | Kra-Tronic Corporation | Arquivos de dados | Mouse And Key Recorder Macro File | Kra-Tronic Corporation Mouse and Key Recorder | Kra-Tronic Corporation |
| .KRF | SPARTA, Inc. | Arquivos de dados | DNSSEC-Tools Keyrec Data File | DNSSEC-Tools | SPARTA, Inc. |
| .KSA | Kubotek Corporation | Arquivos de dados | KeyCreator Settings Archive File | Kubotek USA KeyCreator | Kubotek Corporation |
| .KSM | Pfaff | Arquivos de dados | Pfaff Embroidery Design File Format | Embroidermodder 2 | Open Source |
| .KSP | Luxion | Arquivos de dados | Keyshot Package | Keyshot | Luxion |
| .KSW | Cosmic Patterns Software | Arquivos de dados | Kepler Workflow Document | Kepler | Cosmic Patterns Software |
| .KTE | Open Source | Arquivos de dados | Kite Design File | FoilMaker | Open Source |
| .KTH | Apple | Arquivos de dados | iWork Keynote Theme | Apple Keynote | Apple |
| .KTI | Kelvin TOP-SET | Arquivos de dados | Kelvin TOP-SET Investigator Data | Kelvin TOP-SET Investigator | Kelvin TOP-SET |
| .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 |
| .KUF | K.Y.N.G | Arquivos de dados | K.Y.N.G Update Data | K.Y.N.G | K.Y.N.G |
| .KUU | K.Y.N.G | Arquivos de dados | K.Y.N.G Data File | K.Y.N.G | K.Y.N.G |
| .KVB | MSR Enterprises | Arquivos de dados | Klick-N-View Business Cards | Klick-N-View Business Cards | MSR Enterprises |
| .KVC | Open Source | Arquivos de dados | KVC | KVIrc | Open Source |
| .KW3 | Pacific Software Publishing, Inc. | Arquivos de dados | KanjiWORD Document File | KanjiWORD | Pacific Software Publishing, Inc. |
| .KWB | Open Source | Arquivos de dados | Kwalitan Work File | Kwalitan | Open Source |
| .KWL | KDE | Arquivos de dados | KWalletManager File | KWalletManager | KDE |
| .KWO | KeyWallet GbR | Arquivos de dados | KeyWallet Encrypted Password Storage | KeyWallet | KeyWallet GbR |
| .KWZ | Nintendo | Arquivos de dados | Flipnote Studio 3D Flipnote Data | Flipnote Studio 3D | Nintendo |
| .KXP | SoftKey | Arquivos de dados | KEY Home Gourmet Data | KEY Home Gourmet | SoftKey |
| .KY | Sage | Arquivos de dados | Peachtext List Manager File | Peachtext | Sage |
| .KYN | ESTsoft | Arquivos de dados | ALSee Thumbnail Cache | ALSee | ESTsoft |
| .KZB | Rightware | Arquivos de dados | Kanzi Studio Binary Data | Kanzi Studio | Rightware |
| .L | Johan Bontes | Arquivos de dados | Game Of Life File | Life32 | Johan Bontes |
| .L16 | JRiver | Arquivos de dados | JRiver Media Center File | JRiver Media Center | JRiver |
| .L2P | IBM | Arquivos de dados | IBM Voice Type Languages Addword Data | IBM Voice Type | IBM |
| .L5K | Rockwell Automation Inc. | Arquivos de dados | RSLogix 5000 File | Studio 5000 Logix Designer | Rockwell Automation Inc. |
| .L6T | Line 6 | Arquivos de dados | Line 6 Tone File | Line 6 Gearbox | Line 6 |
| .LA | Open Source | Arquivos de dados | Lossless Audio File | Nullsoft Winamp | Nullsoft |
| .LAB | Corel | Arquivos de dados | WordPerfect Label Definition File | Corel WordPerfect | Corel |
| .LABEL | DYMO | Arquivos de dados | DYMO Label File | DYMO Printers | DYMO |
| .LAC | IBM | Arquivos de dados | Cognos Local Authentication Cache | Cognos software | IBM |
| .LAO | Epson US | Arquivos de dados | EPSON SMART PANEL File | EPSON SMART PANEL | Epson US |
| .LAR | Liquid Audio Inc | Arquivos de dados | Liquid Audio Player Registration File Format | Liquid Audio Player | Liquid Audio Inc |
| .LARGE | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LAS | Various Developers | Arquivos de dados | LIDAR Data Exchange File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .LAST | Valve | Arquivos de dados | Valve Steam Data | Steam | Valve |
| .LASXML | Unknown Developer | Arquivos de dados | Laser App Data Exchange | Unknown Software | Unknown Developer |
| .LAT | Leslie Lamport | Arquivos de dados | LaTeX File | LaTex | Leslie Lamport |
| .LAUNCHER | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LAV | PSU Miller Lab | Arquivos de dados | DNA Sequence Alignment File | LASTZ | PSU Miller Lab |
| .LAVS | Liquid Audio Inc | Arquivos de dados | Liquid Audio Secured Download File | Liquid Audio Player | Liquid Audio Inc |
| .LAW | E*Law Publishing Limited | Arquivos de dados | eLawForms | eLawForms | E*Law Publishing Limited |
| .LAY | Tecplot, Inc | Arquivos de dados | Tecplot Layout File | Tecplot 360 | Tecplot, Inc |
| .LAZ | Global Heavy Industries | Arquivos de dados | LiquidApps Project File | Liquid Studio | Global Heavy Industries |
| .LA_ | Texas Instruments, Inc. | Arquivos de dados | TI Databook File | TI Connect | Texas Instruments, Inc. |
| .LBA | ShopTalk Systems | Arquivos de dados | Liberty BASIC Source Code | Liberty Basic | ShopTalk Systems |
| .LBD | Llamagraphics | Arquivos de dados | Life Balance User Data File | Life Balance | Llamagraphics |
| .LBE | Llamagraphics | Arquivos de dados | Life Balance Xml-based Exchange Data | Life Balance | Llamagraphics |
| .LBL | Interscape | Arquivos de dados | Now Contact Label Template | Now Up-to-Date (Now Contact) | Now Software |
| .LBM | Electronic Arts | Arquivos de dados | Deluxe Paint Bitmap Image File | Canvas X | ACD Systems |
| .LBP | Schneider Electric | Arquivos de dados | ProWORX Nxt Logic Pointer Data | ProWORX | Schneider Electric |
| .LBR | Dag Agren, Circlesoft | Arquivos de dados | LU Library Archive | The Unarchiver | Dag Agren, Circlesoft |
| .LBX | Microsoft Corporation | Arquivos de dados | FoxPro Label File | Microsoft Visual FoxPro | Microsoft Corporation |
| .LBXLLS | Interscape | Arquivos de dados | Logos Libronix 3.0 Data | Logos Bible Software | Interscape |
| .LBXWKS | Libronix Corporation | Arquivos de dados | Libronix DLS Workspace | Digital Library System | Libronix Corporation |
| .LCC | IBM | Arquivos de dados | IBM Voice Type Languages Newuser File | IBM Voice Type | IBM |
| .LCD | ABBYY | Arquivos de dados | ABBYY Language File | ABBYY FineReader | ABBYY |
| .LCN | Microsoft Corporation | Arquivos de dados | License File | Microsoft Windows | Microsoft Corporation |
| .LCP | Mark Finney | Arquivos de dados | FARSITE Landscape Data | FARSITE | Mark Finney |
| .LCS | Swiftpage, Inc. | Arquivos de dados | ACT! History Data | Act! | Swiftpage, Inc. |
| .LCT | Oracle Corporation | Arquivos de dados | Oracle Database Configuration File | Oracle Database | Oracle Corporation |
| .LCX | Cray Inc. | Arquivos de dados | LC Model | Microsoft Notepad | Microsoft Corporation |
| .LD | deltaComm Development Inc | Arquivos de dados | Telix Long Distance Codes Data | Telix for Windows | deltaComm Development Inc |
| .LD2 | Kevin Yau | Arquivos de dados | Lingoes Dictionary File | Lingoes | Kevin Yau |
| .LDF | Microsoft Corporation | Arquivos de dados | SQL Server Transaction Log File | Microsoft SQL Server | Microsoft Corporation |
| .LDIF | Mozilla | Arquivos de dados | LDAP Data Interchange Format File | Mozilla Thunderbird | Mozilla |
| .LDL | Corel Corporation | Arquivos de dados | Corel Paradox Delivered Library File | Corel Paradox | Corel |
| .LDP | Kevin Yau | Arquivos de dados | Lingoes Dictionary File | Lingoes | Kevin Yau |
| .LDS | GNU Project | Arquivos de dados | Binutils LD Linker Script | Microsoft Notepad | Microsoft Corporation |
| .LDT | DIAL | Arquivos de dados | Eulumdat Formatted Luminaire Data File | DIAL DIALux | DIAL |
| .LDX | Global Heavy Industries | Arquivos de dados | Liquid Studio Compiled Executable | Liquid Studio | Global Heavy Industries |
| .LEGAL | DaveTech | Arquivos de dados | DaveTech Legal Document | Notepad++ | Don Ho |
| .LEP | CAM Development | Arquivos de dados | Label and Envelope Designer Plus 2000 Data File | Label and Envelope Designer Plus 2000 | CAM Development |
| .LES | David A. Wheeler | Arquivos de dados | Lesson File | Mklesson | David A. Wheeler |
| .LET | Genesis 2000, Inc | Arquivos de dados | Genesis 2000 Data | Genesis 2000 | Genesis 2000, Inc |
| .LETTER | Proofpoint, Inc. | Arquivos de dados | Undeliverable Mail File | Sendmail | Proofpoint, Inc. |
| .LEV | Interscape | Arquivos de dados | NetHack Level File | NetHack | Interscape |
| .LEX | Adobe Systems Incorporated | Arquivos de dados | Adobe Linguistic Library Data File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .LEXT | Olympus Corporation | Arquivos de dados | Olympus Lext Measurement Export | Unknown Software | Unknown Developer |
| .LF | Concept Software | Arquivos de dados | SoftwareKey License | Protection PLUS | Concept Software |
| .LFB | Laserfiche | Arquivos de dados | Laserfiche Briefcase | Laserfiche Client and Server | Laserfiche |
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