| .MPS | IBM | Pliki z danymi | Mathematical Programming System File | Vim | Bram Moolenaar |
| .MPT | Microsoft Corporation | Pliki z danymi | Microsoft Project Template | Microsoft Project 2016 | Microsoft Corporation |
| .MPX | Microsoft Corporation | Pliki z danymi | FoxPro Compiled Menu Program | Microsoft Visual FoxPro | Microsoft Corporation |
| .MPZ | Benetech | Pliki z danymi | Miradi Project File | Miradi | Benetech |
| .MQD | Open Source | Pliki z danymi | Malete Query Data File | Malete | Open Source |
| .MQP | GoldWave Inc. | Pliki z danymi | Multiquence Project | Multiquence | GoldWave Inc. |
| .MRC | mIRC Co. Ltd | Pliki z danymi | mIRC Script File | mIRC | mIRC Co. Ltd |
| .MRD | Interscape | Pliki z danymi | MathRevolt Infinity Document | Infinity | Interscape |
| .MRF | Apple | Pliki z danymi | Macintosh Font File | Apple OS X | Apple |
| .MRI | Open Source | Pliki z danymi | Pittsburgh MRI File Format | PGH_MRI | Open Source |
| .MRO | Graham Jones | Pliki z danymi | SharpEye Music Reader File | SharpEye Music Reader | Graham Jones |
| .MRP | Interscape | Pliki z danymi | Infinity Solution Plot Data | Infinity | Interscape |
| .MRX | Open Source | Pliki z danymi | Record Access File | Malete | Open Source |
| .MS-ONE-STUB | Microsoft Corporation | Pliki z danymi | Microsoft OneNote Stub Data | Microsoft OneNote | Microsoft Corporation |
| .MS-WINDOWS-STORE-LICENSE | Microsoft Corporation | Pliki z danymi | Microsoft Windows License Manager Data | Microsoft Windows | Microsoft Corporation |
| .MS8 | National Instruments | Pliki z danymi | Multisim 8 Circuit Design File | NI Multisim | National Instruments |
| .MSB | Oracle Corporation | Pliki z danymi | Oracle Binary Message File | Oracle Database | Oracle Corporation |
| .MSC | Microsoft Corporation | Pliki z danymi | Microsoft C Makefile | Microsoft Visual C++ | Microsoft Corporation |
| .MSD | ESRI | Pliki z danymi | Map Service Definition File | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .MSF | Mozilla | Pliki z danymi | Mail Summary File | Mozilla Thunderbird | Mozilla |
| .MSG | Microsoft Corporation | Pliki z danymi | Saved Email Message | Microsoft Outlook Express | Microsoft Corporation |
| .MSG2 | Apple | Pliki z danymi | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .MSIF | Avanquest Software | Pliki z danymi | MyLabel Designer Deluxe Data File | MyLabel Designer Deluxe | Avanquest Software |
| .MSK | Corel | Pliki z danymi | Paint Shop Pro Mask File | PaintShop Pro | Corel |
| .MSN | Microsoft Corporation | Pliki z danymi | Host Blocking File | Microsoft Windows | Microsoft Corporation |
| .MSO | Microsoft Corporation | Pliki z danymi | Microsoft Organization Chart Data File | Microsoft Organization Chart | Microsoft Corporation |
| .MSP | Microsoft Corporation | Pliki z danymi | Windows Installer Patch | Windows Installer | Microsoft Corporation |
| .MSR | Hexagon Mining | Pliki z danymi | MineSight Resource Format File | MineSight 3D | Hexagon Mining |
| .MST | Corel | Pliki z danymi | Corel Presentations Master Template File | Corel Presentations X8 | Corel |
| .MSVC | Microsoft Corporation | Pliki z danymi | Microsoft Visual C++ Compiler Makefile | Microsoft Visual C++ | Microsoft Corporation |
| .MTB | Digistore Solutions | Pliki z danymi | MediaTracker Database Backup File | MediaTracker | Digistore Solutions |
| .MTC | Make The Cut, LLC | Pliki z danymi | Make The Cut! Project | Make the Cut! | Make The Cut, LLC |
| .MTF | Motorola | Pliki z danymi | Motorola Theme File | Motorola MOTOCAST USB | Motorola |
| .MTH | Texas Instruments, Inc. | Pliki z danymi | Derive Math File | Texas Instruments Derive | Texas Instruments, Inc. |
| .MTM | VideoLAN | Pliki z danymi | MultiTracker Module | VLC Media Player | VideoLAN |
| .MTS | Sony | Pliki z danymi | AVCHD Video File | Microsoft Windows Media Player | Microsoft Corporation |
| .MTT | Digital Confidence | Pliki z danymi | MetadataTouch Template | Digital Confidence MetadataTouch | Digital Confidence |
| .MTW | Minitab Inc | Pliki z danymi | Minitab Worksheet File | Minitab | Minitab Inc |
| .MUF | Alpha Software | Pliki z danymi | Alpha Five License File | Alpha Anywhere - Alpha Software | Alpha Software |
| .MUM | AmsterCHEM | Pliki z danymi | MATLAB Unit Operation Model File | AmsterCHEM MATLAB CAPE-OPEN Unit Operation | AmsterCHEM |
| .MUP | Lauriso Software | Pliki z danymi | Music Publisher Score | Music Publisher | Lauriso Software |
| .MVE | BioWare | Pliki z danymi | Infinity Engine Movie File | Baldur's Gate | BioWare |
| .MVP | Magix Software GmbH | Pliki z danymi | MAGIX Video Project File | MAGIX Video Pro X | Magix Software GmbH |
| .MW | Apple | Pliki z danymi | MacWrite Text Document | MacWrite | Apple |
| .MWF | Autodesk, Inc. | Pliki z danymi | MapGuide Author Map Window File | Infrastructure Map Server | Autodesk, Inc. |
| .MWS | Waterloo Maple, Inc. (Maplesoft) | Pliki z danymi | Maple Classic Worksheet | Maple | Waterloo Maple, Inc. (Maplesoft) |
| .MWV | Unknown Developer | Pliki z danymi | Media Works Data | Unknown Software | Unknown Developer |
| .MX | Wolfram Research | Pliki z danymi | Mathematica Serialized Package File | Wolfram Research Mathematica | Wolfram Research |
| .MXC2 | Magix Software GmbH | Pliki z danymi | MAGIX Cache File | MAGIX Music Maker | Magix Software GmbH |
| .MXI | Adobe Systems Incorporated | Pliki z danymi | Adobe Extension Information File | Adobe InCopy | Adobe Systems Incorporated |
| .MXM | Next Limit Technologies | Pliki z danymi | Maxwell Material File | Maxwell Render | Next Limit Technologies |
| .MXP | Adobe Systems Incorporated | Pliki z danymi | Adobe Extension Package | Adobe Extension Manager CC | Adobe Systems Incorporated |
| .MYB | MYOB Limited | Pliki z danymi | MYOB Data File | MyOB | MYOB Limited |
| .MYI | Oracle Corporation | Pliki z danymi | MySQL MyISAM Index File | MySQL | Oracle Corporation |
| .MYO | Acclivity LLC | Pliki z danymi | AccountEdge Company File | AccountEdge Pro | Acclivity LLC |
| .MZE | Gregory Peatfield | Pliki z danymi | Maze Creator File | Maze Creator | Gregory Peatfield |
| .MZT | David Webber | Pliki z danymi | MOZART Template File | Mozart | David Webber |
| .MZV | Viewpoint Corporation | Pliki z danymi | Viewpoint Media Player ZoomView File | Viewpoint Media Player | Viewpoint Corporation |
| .MZX | MegaZeux Developers | Pliki z danymi | MegaZeux Data | MegaZeux | MegaZeux Developers |
| .N1 | Symantec Corporation | Pliki z danymi | Nuke Randomic Life Generator File | AVG Antivirus | AVG Technologies |
| .N2P | Unknown Developer | Pliki z danymi | Net2Phone Data | Net2Phone | Unknown Developer |
| .NAD | Malcolm Sambridge | Pliki z danymi | Neighbourhood Algorithm | na-bayes | Malcolm Sambridge |
| .NAF | Native Instruments | Pliki z danymi | TRAKTOR Service Data File | Traktor | Native Instruments |
| .NAI | Unknown Developer | Pliki z danymi | WinINSTALL Data | Unknown Software | Unknown Developer |
| .NAL | Novell, Inc. | Pliki z danymi | Novell ZENworks Suite Network Delivered Application Shortcut File Format | ZENworks Suite | Novell, Inc. |
| .NAM | Aqua-3D | Pliki z danymi | Aqua3D Network File | Aqua3D | Unknown Developer |
| .NAMES | Apple | Pliki z danymi | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .NAP | McAfee, Inc. | Pliki z danymi | McAfee ePO Network Associates Package | McAfee ePolicy Orchestrator | McAfee, Inc. |
| .NAS | MSC Software | Pliki z danymi | Nastran Input File | MSC Nastran | MSC Software |
| .NASL | Tenable | Pliki z danymi | Nessus Attack Scripting Language Key File | Nessus | Tenable |
| .NATVIS | Microsoft Corporation | Pliki z danymi | Microsoft Visual Studio Text Data | Microsoft Visual Studio | Microsoft Corporation |
| .NBE | Tenable | Pliki z danymi | Nessus Report File | Nessus | Tenable |
| .NBK | SMART Technologies | Pliki z danymi | SMART Notebook File | MimioStudio | Mimio |
| .NBP | Wolfram Research | Pliki z danymi | Mathematica Player Notebook File | Wolfram Research Mathematica | Wolfram Research |
| .NC | CNC Software | Pliki z danymi | Mastercam Numerical Control File | Mastercam | CNC Software |
| .NCC | Robert A. Pemberton | Pliki z danymi | CamView 3D File | CamView 3D | Robert A. Pemberton |
| .NCE | Miroslav Rajčić | Pliki z danymi | NoteCase Pro Encrypted Document | NoteCase Pro | Miroslav Rajčić |
| .NCF | Valve | Pliki z danymi | No Cache File | GCFScape | Open Source |
| .NCG | Native Instruments | Pliki z danymi | Native Instruments Controller Editor Template | Controller Editor | Native Instruments |
| .NCT | Interscape | Pliki z danymi | Now Contact File | Now Up-to-Date (Now Contact) | Now Software |
| .NDB | Naviter | Pliki z danymi | SeeYou Waypoint File | SeeYou | Naviter |
| .NDF | Microsoft Corporation | Pliki z danymi | SQL Server Secondary Database File | Microsoft SQL Server | Microsoft Corporation |
| .NDK | IBM | Pliki z danymi | Lotus Notes Design Elements File | IBM Lotus Notes | IBM |
| .NDM | PremiumSoft CyberTech Ltd | Pliki z danymi | Navicat Data Modeler Database Model | Navicat for MySQL | PremiumSoft CyberTech Ltd |
| .NDR | Nikon | Pliki z danymi | Nikon Capture Image Dust Off File | Nikon Capture NX | Nikon |
| .NDS | Nintendo | Pliki z danymi | Nintendo DS Game ROM | No Cash GBA (No$GBA) | Martin Korth |
| .NDT | NEPLAN AG | Pliki z danymi | NEPLAN External Program Import/ Export File | NEPLAN Electricity | NEPLAN AG |
| .NDV | Exelis Inc. | Pliki z danymi | ENVI N-D Visualizer State Data | ENVI | Exelis Inc. |
| .NDX | Unknown Developer | Pliki z danymi | dBASE Index File | Microsoft Visual FoxPro | Microsoft Corporation |
| .NEC | W7EL | Pliki z danymi | NEC Antenna Data | EZNEC | W7EL |
| .NED | OpenSim Ltd | Pliki z danymi | OMNeT++ Network Description File | OMNeT++ | OpenSim Ltd |
| .NET | Netviz LLC | Pliki z danymi | NetViz Project File | netViz Enterprise software | Netviz LLC |
| .NETA | Norsys Software Corp | Pliki z danymi | Netica Binary File | Norsys Netica | Norsys Software Corp |
| .NETCDF | University Corporation for Atmospheric Research (UCAR) | Pliki z danymi | Scientific Data NETwork Common Data Format | Ferret | NOAA |
| .NEX | Opera Software | Pliki z danymi | Navigator Extension | Opera | Opera Software |
| .NF | Unknown Developer | Pliki z danymi | CVIP NF_help File | Unknown Software | Unknown Developer |
| .NF2 | National Creative Registry | Pliki z danymi | NeverForget Data File | NeverForget | National Creative Registry |
| .NFI | Dream Multimedia | Pliki z danymi | Dreambox Disc Image | FlashWizard PRO | DreamLogic Software |
| .NFL | Nokia | Pliki z danymi | Nokia Flash Lite Package | WinRAR | Eugene Roshal |
| .NFO | Microsoft Corporation | Pliki z danymi | System Information File | Microsoft System Information | Microsoft Corporation |
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