| .MSG | Microsoft Corporation | Spieldateien | Saved Email Message | Microsoft Outlook Express | Microsoft Corporation |
| .MSH | Martin Schweiger | Spieldateien | Orbiter 3D Mesh File | Orbiter | Martin Schweiger |
| .MSN | Microsoft Corporation | Spieldateien | Host Blocking File | Microsoft Windows | Microsoft Corporation |
| .MSX | Microsoft Corporation | Spieldateien | Age Of Empires II Saved Game | Microsoft Age of Empires | Ensemble Studios |
| .MT | Simtex Studios Inc. | Spieldateien | 1830 Railroads And Robber Barons Game Data | 1830: Railroads & Robber Barons | Simtex Studios Inc. |
| .MTR | Knife Edge Software | Spieldateien | RealFight Radio Control File | RealFlight | Knife Edge Software |
| .MTV | MyMPX.org | Spieldateien | MTV Video Format File | ShedWorx Smart Converter | Shedworx |
| .MUL | OriginLab | Spieldateien | Ultima Online Multi File | MULTool | Interscape |
| .MUS | MakeMusic, Inc. | Spieldateien | Finale Notation File | SmartMusic | MakeMusic, Inc. |
| .MW0 | Nintendo | Spieldateien | Super Mario World File | Super Mario World | Nintendo |
| .MW4 | Activision | Spieldateien | MechWarrior Game Structure File Archive | MechWarrior 2: Mercenaries | Activision |
| .MWM | Keen Software House | Spieldateien | Space Engineers Model | Space Engineers | Keen Software House |
| .MYS | Vineyard Technologies | Spieldateien | Vineyard Captured Video File | Vineyard Technologies PC Viewer | Vineyard Technologies |
| .MYT | Burkhard Renk | Spieldateien | AI Aircraft Traffic Database File | MyTraffic X | Burkhard Renk |
| .N2E | NeocoreGames | Spieldateien | The Incredible Adventures Of Van Helsing Effects | The Incredible Adventures of Van Helsing | NeocoreGames |
| .N2PK | NeocoreGames | Spieldateien | The Incredible Adventures Of Van Helsing Game Data File | The Incredible Adventures of Van Helsing | NeocoreGames |
| .N64 | Unknown Developer | Spieldateien | Nintendo 64 Emulator ROM File | Project64 | Open Source |
| .NAM | Aqua-3D | Spieldateien | Aqua3D Network File | Aqua3D | Unknown Developer |
| .NAR | Nexon | Spieldateien | Nexon Game Archive | Counter-Strike Online | Nexon |
| .NARC | Nintendo | Spieldateien | Nintendo DS Archive File | MKDS Course Modifier | Gericom |
| .NAV | Valve | Spieldateien | Id Tech 3 Bot Navigation File | Quake 3 Arena | id Software |
| .NAZ | Deadline Games | Spieldateien | Total Overdose Game Data File | Deadline Games Total Overdose | Deadline Games |
| .NCF | Valve | Spieldateien | No Cache File | GCFScape | Open Source |
| .NCP | Nikon | Spieldateien | Nikon Camera Photo Settings | Nikon ViewNX | Nikon |
| .NDS | Nintendo | Spieldateien | Nintendo DS Game ROM | No Cash GBA (No$GBA) | Martin Korth |
| .NEBULA | Sierra Entertainment | Spieldateien | Nebula Data | Homeworld 2 | Sierra Entertainment |
| .NES | Nintendo | Spieldateien | Nintendo (NES) ROM File | Jnes | Jabosoft |
| .NFG | Open Source | Spieldateien | NewsBin Configuration File | DJI Interprises NewsBin Pro | Open Source |
| .NFO | Microsoft Corporation | Spieldateien | System Information File | Microsoft System Information | Microsoft Corporation |
| .NFS | Codemasters | Spieldateien | F1 2015 Speech Data | F1 2015 | Codemasters |
| .NFS13SAVE | Electronic Arts | Spieldateien | Need For Speed: Most Wanted Saved Game Position | Need For Speed | Electronic Arts |
| .NGB | Alexander S. Meshcheryakov | Spieldateien | Nonogram Puzzle Data | QNonograms | Alexander S. Meshcheryakov |
| .NGN | Terminal Reality | Spieldateien | Fly! Engine Specification | Fly! | Terminal Reality |
| .NGP | Richard Bannister | Spieldateien | Neo Geo Pocket ROM Image | Neopocott v0.5.2 | Richard Bannister |
| .NGS | 5pb. and Nitroplus | Spieldateien | Steins;Gate Game File | Steins;Gate | 5pb. and Nitroplus |
| .NH | Interscape | Spieldateien | NetHack Game Configuration File | NetHack | Interscape |
| .NIS | Sierra Entertainment | Spieldateien | Homeworld Non-Interactive Sequence | Homeworld 2 | Sierra Entertainment |
| .NKM | Native Instruments | Spieldateien | Kontakt Multi Instrument File | Native Instruments Kontakt | Native Instruments |
| .NLB | Oracle Corporation | Spieldateien | Oracle Locale Builder Binary File | Oracle Locale Builder | Oracle Corporation |
| .NLTRACK | Mad Data | Spieldateien | NoLimits Roller Coaster Track File | NoLimits | Mad Data |
| .NML | Native Instruments | Spieldateien | Traktor Collection File | Traktor | Native Instruments |
| .NMM | Microsoft Corporation | Spieldateien | Microsoft 3D Movie Maker Recorded Video | 3D Movie Maker | Microsoft Corporation |
| .NOB | Infogrames | Spieldateien | Silver Game Data | Silver | Infogrames |
| .NON | Totally Games | Spieldateien | Star Wars: Tie Fighter Mouse Options File | Star Wars: TIE Fighter | LucasArts Entertainment Company, LLC |
| .NPA | 5pb. and Nitroplus | Spieldateien | Steins;Gate Archive File | Steins;Gate | 5pb. and Nitroplus |
| .NPC | Nikon | Spieldateien | Picture Control Utility Picture Control File | Picture Control Utility | Nikon |
| .NS1 | Open Source | Spieldateien | Nestopia Save State | Nestopia | Open Source |
| .NSM | Unknown Developer | Spieldateien | NESticle Movie | Unknown Software | Unknown Developer |
| .NSS | Perion Network Ltd | Spieldateien | Magentic Screensaver File | IncrediMail | Perion Network Ltd |
| .NTL | Blizzard Entertainment Inc. | Spieldateien | Diablo 2 Mod D2NT Script | Diablo II | Blizzard Entertainment Inc. |
| .NTRK | Ubisoft | Spieldateien | Pacific FIghters Online Track File | Pacific Fighters | Ubisoft Blue Byte |
| .NUT | Open Source | Spieldateien | NUT Video File | MPlayer | The MPlayer Team |
| .NV | Q.W.Page Associates Inc | Spieldateien | NewViews Database File | Q.W. Page NewViews 2 | Q.W.Page Associates Inc |
| .NVT | Neuralynx | Spieldateien | NeuraLynx Video Tracker Data | Video Tracker File Playback | Neuralynx |
| .NWX | LucasArts Entertainment Company, LLC | Spieldateien | Outlaws Choreography File | Outlaws | LucasArts Entertainment Company, LLC |
| .NX | Nexon | Spieldateien | MapleStory NX Package | MapleStroy | Nexon |
| .OBS | Department of Wind Energy at the Technical University of Denmark, Denmark | Spieldateien | WAsP Obstacle List Data | WAsP | Department of Wind Energy at the Technical University of Denmark, Denmark |
| .ODF | Oracle Corporation | Spieldateien | OpenDocument Formula | Apache OpenOffice | Apache Software Foundation |
| .OMOD | Bethesda Softworks | Spieldateien | Oblivion Mod Archive | The Elder Scrolls IV: Oblivion | Bethesda Softworks |
| .OOB | Matrix Games | Spieldateien | Steel Panthers World At War Data | Steel Panthers: World At War | Matrix Games |
| .OPA | Terminal Reality | Spieldateien | Fly! RAW Image Opacity Map File | Fly! | Terminal Reality |
| .OPN | Rebel Software | Spieldateien | Rebel Strip Poker Opponent Data | Amature Strip Poker | Unknown Developer |
| .OPT | LexisNexis | Spieldateien | Concordance Database File | LexisNexis Concordance | LexisNexis |
| .ORE | Crait Corp. | Spieldateien | Ore Executable File | Ore Runtime Environment | Jonathan Holmes |
| .ORI | Unknown Developer | Spieldateien | Original File | Unknown Software | Unknown Developer |
| .ORK | Relic Entertainment | Spieldateien | Warhammer Mark Of Chaos Game Archive | Warhammer 40K Dawn of War | Relic Entertainment |
| .OSC | OpenStreetMap | Spieldateien | OpenStreetMap Change File | Merkaartor | Bart Vanhauwaert, Chris Browet, Ladislav Láska, and others |
| .OSF | Interplay Entertainment | Spieldateien | Descent 3 Sound Data | Descent 3 | Interplay Entertainment |
| .OSR | Ppy Pty Ltd | Spieldateien | Osu! Game Replay | osu! | Ppy Pty Ltd |
| .OSZ | Ppy Pty Ltd | Spieldateien | Osu! Beatmap File | osu! | Ppy Pty Ltd |
| .OTD | Open Source | Spieldateien | OpenIV Texture Data | OpenIV | Open Source |
| .OVL | Atari Corporation | Spieldateien | Rollercoaster Tycoon 3 Data File | RollerCoaster Tycoon 3 | Frontier Developments plc |
| .P000 | Runewaker Entertainment | Spieldateien | Dragon's Prophet Game Data | Dragon's Prophet | Runewaker Entertainment |
| .P2M | Dassault Systèmes | Spieldateien | PhotoWorks Appearance File | SFW PhotoWorks | Seattle Lab |
| .P3T | Sony | Spieldateien | PlayStation 3 Theme File | P3T Unpacker | Open Source |
| .P8 | Lexaloffle Games | Spieldateien | PICO-8 Data | PICO-8 | Lexaloffle Games |
| .PACK | neOceane | Spieldateien | CustoPack Tools Theme Pack | CustoPack Tools | neOceane |
| .PACKAGE | Electronic Arts | Spieldateien | Electronic Arts Game Package File | Electronic Arts The Sims 2 | Electronic Arts |
| .PACKED | Codemasters | Spieldateien | Jericho Game Data | Clive Barker's Jericho | Codemasters |
| .PAK | Unknown Developer | Spieldateien | Video Game Package | Dragon UnPACKer | Open Source |
| .PAR | Siemens PLM Software | Spieldateien | Solid Edge Part File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .PAT | Autodesk, Inc. | Spieldateien | AutoCAD Hatch Pattern File | Autodesk AutoCAD | Autodesk, Inc. |
| .PAZ | PEARL FOUNDATION | Spieldateien | Black Desert Game Data | Black Desert Online | PEARL FOUNDATION |
| .PBN | Open Source | Spieldateien | Portable Bridge Notation File | RoboBridge | Open Source |
| .PBO | Bohemia Interactive | Spieldateien | Packed Bohemia Object | ArmA: Armed Assault | Bohemia Interactive |
| .PBP | Sony | Spieldateien | PSP Firmware Update File | PBP Unpacker | Unknown Developer |
| .PCC | Electronic Arts | Spieldateien | Mass Effect Package | Mass Effect 3 | BioWare |
| .PCD | PokéCheats | Spieldateien | Pokémon Wonder Card File | Pokesav | PokéCheats |
| .PCE | Open Source | Spieldateien | TurboGrafx-16 ROM | Magic Engine | Open Source |
| .PCF | Blackstrip Studios | Spieldateien | PaintCAD Font | PaintCAD | Blackstrip Studios |
| .PCK | Microsoft Corporation | Spieldateien | System Center Configuration Manager Package File | Microsoft system center configuration manager | Microsoft Corporation |
| .PCP | Microsoft Corporation | Spieldateien | Windows Installer Patch Creation Properties File | Microsoft Windows SDK | Microsoft Corporation |
| .PDA | Molecular Devices | Spieldateien | SoftMax Pro Microplate Data Analysis File | SoftMax Pro | Molecular Devices |
| .PDT | Microsoft Corporation | Spieldateien | InkWriter Note Taker Template File | Windows Mobile | Microsoft Corporation |
| .PEG | PopCap Games | Spieldateien | Peggle Replay File | Peggle | PopCap Games |
| .PEO | Relic Entertainment | Spieldateien | Homeworld MESH File | Homeworld | Relic Entertainment |
| .PER | Microsoft Corporation | Spieldateien | Age Of Empires Personality File | Microsoft Notepad | Microsoft Corporation |
| .PFF | Access | Spieldateien | Formatta Portable Form File | Access Formatta Filler | Access |
| .PGB | Ubisoft | Spieldateien | Rayman 2 Game Data | Rayman 2: The Great Escape | Ubisoft |
| .PGE | Open Source | Spieldateien | PocketGrandmaster Engine File | PocketGrandmaster | Open Source |
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