| .LBU | Interscape | Asetustiedostot | Cloaked Affiliate Link Builder Settings File | Cloaked Affiliate Link Builder | Interscape |
| .LCC | IBM | Asetustiedostot | IBM Voice Type Languages Newuser File | IBM Voice Type | IBM |
| .LED | Sony | Asetustiedostot | Sony AIBO LED Lights Control Data | Unknown Software | Unknown Developer |
| .LENS | Autodesk, Inc. | Asetustiedostot | Autodesk Stitcher Camera Profile | Autodesk Stitcher Unlimited | Autodesk, Inc. |
| .LES | David A. Wheeler | Asetustiedostot | Lesson File | Mklesson | David A. Wheeler |
| .LF | Concept Software | Asetustiedostot | SoftwareKey License | Protection PLUS | Concept Software |
| .LGT | Microsoft Corporation | Asetustiedostot | Let's Go! Theme File | Let's Go! | Microsoft Corporation |
| .LH3D | BeLight Software | Asetustiedostot | Live Home 3D Project | Live Home 3D | BeLight Software |
| .LIC | Unknown Developer | Asetustiedostot | Software License File | Microsoft Visual C++ | Microsoft Corporation |
| .LIR | Applied Digital | Asetustiedostot | ADI Ocelot Settings File | C-Max | Applied Digital |
| .LKF | PCS Systemtechnik GmbH | Asetustiedostot | INTUS Terminal Keyboard Settings | INTUS 5600 MULTIFUNCTIONAL TERMINAL | PCS Systemtechnik GmbH |
| .LKG | Hewlett-Packard | Asetustiedostot | HP-UX Configuration Data | HP-UX 11i Web Server Suite | Hewlett-Packard |
| .LLC | LapLink Software | Asetustiedostot | LapLink Saved Connection File | LapLink | LapLink Software |
| .LLP | General Electric Company | Asetustiedostot | VersaPro Local Logic Block | VersaPro | General Electric Company |
| .LOCAL | Embarcadero Technologies | Asetustiedostot | Delphi User-Specific Project Options | Delphi (IDE) | Embarcadero Technologies |
| .LOOK | Adobe Systems Incorporated | Asetustiedostot | SpeedGrade Look File | Adobe SpeedGrade | Adobe Systems Incorporated |
| .LOP | ValuSoft | Asetustiedostot | MasterCook Layout File | ValuSoft MasterCook | ValuSoft |
| .LSV | Light-O-Rama | Asetustiedostot | Light-O-Rama Sequence Editor Visual Preference File | Light-O-Rama | Light-O-Rama |
| .LSW | Technics | Asetustiedostot | Technics Keyboard Current Panel File | Unknown Software | Unknown Developer |
| .LT | Andrew Jewett | Asetustiedostot | Moltemplate Data File | Moltemplate | Andrew Jewett |
| .LVA | Logitech | Asetustiedostot | Logitech Video Effects Avatar File | Logitech Webcam Software | Logitech |
| .LVF | Logitech | Asetustiedostot | Logitech Video Effects File | Logitech Webcam Software | Logitech |
| .LVT | Open Source | Asetustiedostot | Land Surface Verification Toolkit Configuration | Land Information System Verification Toolkit (LVT) | Open Source |
| .LWL | Johm Mackernon Software | Asetustiedostot | Lightwright Printed Paperwork Formatting Instructions Data | LightWright | Johm Mackernon Software |
| .LX | IBM | Asetustiedostot | LPEX Customization Command Profile File | LPX Editor | IBM |
| .LYT | Adminsoft | Asetustiedostot | Adminsoft Document Layout File | Adminsoft | Adminsoft |
| .M2D | HTC | Asetustiedostot | HTC Manila 2D For Windows Mobile Skin | Windows Mobile | Microsoft Corporation |
| .M2F | Maxthon | Asetustiedostot | Maxthon Filter Package Data | Maxthon Cloud Browser | Maxthon |
| .M2S | Maxthon | Asetustiedostot | Maxthon 2 Browser Skin File | Maxthon Cloud Browser | Maxthon |
| .MAILHOST | Microsoft Corporation | Asetustiedostot | MSN Mailhost Settings File | MSN Explorer | Microsoft Corporation |
| .MAL | Open Source | Asetustiedostot | MadAppLauncher Configuration File | MadAppLauncher | Open Source |
| .MASK | Adobe Systems Incorporated | Asetustiedostot | SpeedGrade Color Mask File | Adobe SpeedGrade | Adobe Systems Incorporated |
| .MBL | Vernier Software & Technology | Asetustiedostot | Logger Pro Data File | Vernier Logger Pro | Vernier Software & Technology |
| .MCE | Sony | Asetustiedostot | Sony CAV-M1000ES Common Source Infrared Command File | Sony CAV-M1000ES | Sony |
| .MCH | Interscape | Asetustiedostot | Machinery HDR Effects | Machinery HDR | Interscape |
| .MCL | Microsoft Corporation | Asetustiedostot | Windows Media Center Link File | Microsoft Windows Media Player | Microsoft Corporation |
| .MCV | Visicom Media Inc | Asetustiedostot | ManyCam Effect File | ManyCam | Visicom Media Inc |
| .MDP | Microsoft Corporation | Asetustiedostot | Visual C++ 5 Workspace File | Microsoft Visual C++ | Microsoft Corporation |
| .MDS | SmartBear | Asetustiedostot | TestComplete Project File | TestComplete | SmartBear |
| .MDV | Open Source | Asetustiedostot | QLAY MDV Image | QLAY | Open Source |
| .MD_ | Unknown Developer | Asetustiedostot | Visc15 Adressen Setup File | Unknown Software | Unknown Developer |
| .MEF | Microsoft Corporation | Asetustiedostot | Mamiya RAW Image | ACD Systems ACDSee | ACD Systems |
| .MGK | ImageMagick Studio LLC | Asetustiedostot | ImageMagick Configuration File | ImageMagick | ImageMagick Studio LLC |
| .MHC | Microchip Technology Inc. | Asetustiedostot | MPLAB Harmony Configuration Data | MPLAB Harmony | Microchip Technology Inc. |
| .MIX | Microsoft Corporation | Asetustiedostot | Microsoft Image Exchange File | Microsoft Picture It! | Microsoft Corporation |
| .MKS | Matroska | Asetustiedostot | Matroska Elementary Stream File | The Core Media Player | Open Source |
| .MLB | Avanquest Software | Asetustiedostot | MyLabel Designer Deluxe Project File | MyLabel Designer Deluxe | Avanquest Software |
| .MLC | Microsoft Corporation | Asetustiedostot | Microsoft Language Interface Pack | Microsoft Windows | Microsoft Corporation |
| .MLK | ValuSoft | Asetustiedostot | MasterCook Look File | Mastercook Cookbook | Cosmi Finance LLC |
| .MM4 | Microsoft Corporation | Asetustiedostot | Microsoft Windows Word Processing Format | Microsoft Windows | Microsoft Corporation |
| .MMF | Microsoft Corporation | Asetustiedostot | Microsoft Message File | Microsoft Exchange Server | Microsoft Corporation |
| .MMG | Moritz Bunkus | Asetustiedostot | MKVToolNix Muxing Settings | MKVtoolnix | Interscape |
| .MMH | BioWare | Asetustiedostot | Dragon Age Model Mesh Heirarchy File | Dragon Age Toolset | BioWare |
| .MMP | MixMeister Technology | Asetustiedostot | MixMeister Studio Playlist | MixMeister Studio | MixMeister Technology |
| .MMZ | CREAF and UAB | Asetustiedostot | MiraMon Compressed Map File | MiraMon | CREAF and UAB |
| .MNS | Autodesk, Inc. | Asetustiedostot | AutoCAD Interface Settings File | Autodesk AutoCAD | Autodesk, Inc. |
| .MNU | Autodesk, Inc. | Asetustiedostot | AutoCAD Interface Layout File | Microsoft Notepad | Microsoft Corporation |
| .MO | Dassault Systèmes | Asetustiedostot | Dymola Simulation File | Dymola | Dassault Systèmes |
| .MOF | Microsoft Corporation | Asetustiedostot | Managed Object Format File | Microsoft Systems Management Server | Microsoft Corporation |
| .MPW | Microsoft Corporation | Asetustiedostot | Microsoft Project Workspace File | Microsoft Project 2016 | Microsoft Corporation |
| .MSF | Mozilla | Asetustiedostot | Mail Summary File | Mozilla Thunderbird | Mozilla |
| .MSH1XML | Microsoft Corporation | Asetustiedostot | Monad Display Configuration File | Microsoft Notepad | Microsoft Corporation |
| .MSL | Microsoft Corporation | Asetustiedostot | Mapping Specification Language File | Microsoft Notepad | Microsoft Corporation |
| .MSM | Microsoft Corporation | Asetustiedostot | Windows Installer Merge Module | Windows Installer | Microsoft Corporation |
| .MSN | Microsoft Corporation | Asetustiedostot | Host Blocking File | Microsoft Windows | Microsoft Corporation |
| .MST | Corel | Asetustiedostot | Corel Presentations Master Template File | Corel Presentations X8 | Corel |
| .MSW | Corel | Asetustiedostot | Painter Color Mixer Swatches File | Corel Painter | Corel |
| .MSZ | Ventis Media Inc. | Asetustiedostot | MediaMonkey Skin | MediaMonkey | Ventis Media Inc. |
| .MTF | Motorola | Asetustiedostot | Motorola Theme File | Motorola MOTOCAST USB | Motorola |
| .MTT | Digital Confidence | Asetustiedostot | MetadataTouch Template | Digital Confidence MetadataTouch | Digital Confidence |
| .MU | Squad | Asetustiedostot | Kerbal Space Program Mesh File | Squad Kerbal Space Program | Squad |
| .MUD | Autodesk, Inc. | Asetustiedostot | Mudbox 3D Scene File | Autodesk Mudbox 2017 | Autodesk, Inc. |
| .MXS | Next Limit Technologies | Asetustiedostot | Maxwell Studio Scene File | Maxwell Render | Next Limit Technologies |
| .N2S | Acustica Audio | Asetustiedostot | Nebula Skin | Nebula | NeocoreGames |
| .NCB | Microsoft Corporation | Asetustiedostot | Visual C++ IntelliSense Database | Microsoft Visual Studio | Microsoft Corporation |
| .NCM | Nokia | Asetustiedostot | Nokia Communicator Configuration Message | Nokia Suite | Nokia |
| .NCP | Nikon | Asetustiedostot | Nikon Camera Photo Settings | Nikon ViewNX | Nikon |
| .NDC | IBM | Asetustiedostot | Personal Communications Settings File | IBM Personal Communications | IBM |
| .NFG | Open Source | Asetustiedostot | NewsBin Configuration File | DJI Interprises NewsBin Pro | Open Source |
| .NL | Kdan Mobile Software Ltd | Asetustiedostot | Note Ledge File | NoteLedge | Kdan Mobile Software Ltd |
| .NNR | Nikon | Asetustiedostot | Nikon Capture Noise Reduction File | Nikon Capture NX | Nikon |
| .NPC | Nikon | Asetustiedostot | Picture Control Utility Picture Control File | Picture Control Utility | Nikon |
| .NPD | Netrosoft Corporation | Asetustiedostot | Netrosoft Presentation Document | Netrosoft Office Suite | Netrosoft Corporation |
| .NPL | Nokia | Asetustiedostot | Nokia Playlist File | Nokia Multimedia Player | Nokia |
| .NPS | Open Source | Asetustiedostot | Natron Node Presets File | Natron | Open Source |
| .NPT | Extensis | Asetustiedostot | Portfolio NetPublish Pre-cursor Template File | Portfolio | Extensis |
| .NSD | Symantec Corporation | Asetustiedostot | Norton System Doctor Sensor Configuration | Norton SystemWorks | Symantec Corporation |
| .NSX | NS Basic | Asetustiedostot | AppStudio Project | NS Basic AppStudio | NS Basic |
| .NTC | Nikon | Asetustiedostot | Camera Control Pro Custom Curves File | Nikon camera Control Pro | Nikon |
| .NTS | IBM | Asetustiedostot | Lotus Notes Traveler Server Config File | IBM Notes Traveler | IBM |
| .NVC | Nero AG | Asetustiedostot | NeroVision Express Project File | Nero Video 2017 | Nero AG |
| .NVP | QSR International | Asetustiedostot | NVivo For Windows Project | NVivo | QSR International |
| .NWV | Nuance | Asetustiedostot | Dragon NaturallySpeaking User Archive | Nuance Dragon NaturallySpeaking Home 13 | Nuance |
| .OBI | Microsoft Corporation | Asetustiedostot | Outlook RSS Subscription File | Microsoft Outlook 2016 | Microsoft Corporation |
| .OBT | Open Source | Asetustiedostot | Openbox Theme File | Openbox | Open Source |
| .OCE | Oracle Corporation | Asetustiedostot | Open Catalog Extension Connection File | Oracle Business Intelligence Suite | Oracle Corporation |
| .ODC | Microsoft Corporation | Asetustiedostot | Office Data Connection File | Microsoft Excel | Microsoft Corporation |
| .OEM | Microsoft Corporation | Asetustiedostot | Original Equipment Manufacturer Setup File | Microsoft Windows | Microsoft Corporation |
| .OFD | Cypresslogic Systems Inc. | Asetustiedostot | ObjectView Form Definition Data | ObjectView | Cypresslogic Systems Inc. |
| .OFFICEUI | Microsoft Corporation | Asetustiedostot | Microsoft Office UI Customization File | Microsoft Office | Microsoft Corporation |
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