| M | Program file (Matlab) |
| M | Macro module (Brief) |
| M | Standard package (Mathematica) |
| M11 | Text file (MASS11) |
| M1V | MPEG-related file (MIME type 'mpeg') |
| M3 | source code file (Modula 3) |
| M3D | 3D animation (Corel Motion) |
| M3U | MPEG URL (MIME audio file) (MP3 Playlist) |
| M4 | M4 Preprocessor file (Unix) |
| M_U | Hard Drive Boot sector backup (MazeGold) |
| MA3 | Macro (Harvard Graphics 3.0) |
| MAC | Image (MacPaint) |
| MAC | Macro (Generic) |
| MAD | Module (Microsoft Access) |
| MAF | Form (Microsoft Access) |
| MAG | A graphics format found in some Japanese files |
| MAG | MAG graphics format created by Woody Lynn (MPS Magro Paint System) |
| MAGIC | Configuration file (Magic Mail Monitor) |
| MAI | Mail (VAX) |
| MAK | Project (Visual Basic or Microsoft C++) |
| MAK | Makefile (Generic) |
| MAM | Macro (Microsoft Access) |
| MAN | Manual page output (Unix) |
| MAN | Command module (Unix) |
| MAP | Map file (Generic) |
| MAP | WAD game file (Duke Nukem 3D) |
| MAP | Color pallette (Generic) |
| MAP | Format data (Micrografx Picture Publisher) |
| MAP | Linker map file |
| MAP | Map file used for color choices (Pro/Engineer) |
| MAP | Map file (Atlas MapMaker) |
| MAP | Network map (AccView) |
| MAQ | Query (Microsoft Access) |
| MAR | Report (Microsoft Access) |
| MAR | Assembly program (VAX Macro) |
| MAR | Archive (Microstation) |
| MAS | Graphics file (Lotus Freelance Smartmaster) |
| MAT | Binary file (Matlab) |
| MAT | Table (Microsoft Access) |
| MAUD | Sample format (Maud) |
| MAX | 3D scene (Kinetix 3D Studio Max) |
| MAX | Document (Paperport) |
| MAX | Layout file (OrCad) |
| MAX | Source code (MAX) |
| MAZ | Maze data file (Hover) |
| MAZ | A format use by Division's dVS/dVISE |
| MB | Memo field values for database (Paradox) |
| MB1 | Data file (Apogee Monster Bash) |
| MBK | Multiple index archive (dBase IV) |
| MBOX | Mailbox file (Berkeley Unix) |
| MBX | Extension Microsoft Outlook adds to saved email, Eudora mailboxes |
| MCC | Calling card (Dialer10) |
| MCC | Configuration file (MathCad) |
| MCD | Document (MathCad) |
| MCF | Font file (MathCad) |
| MCF | Magic control file |
| MCI | Command script (Media Control Interface) |
| MCP | Project file (Metrowerks CodeWarrior) |
| MCP | Application script (Capsule) |
| MCP | Printer driver (MathCad) |
| MCR | Keyboard macro file (DataCad) |
| MCW | Document (Microsoft Word for Macintosh) |
| MCW | Text document (MacWrite II) |
| MD | Compressed archive (MDCD) |
| MDA | Add-in file (Microsoft Access) |
| MDA | Workgroup (Microsoft Access version 2) |
| MDB | Database (Microsoft Access) |
| MDE | MDE file (Microsoft Access) |
| MDL | Spreadsheet (CA-Compete!) |
| MDL | Music module (MOD) (Digital Trakker) |
| MDL | Model (3D Design Plus) |
| MDL | Model file (Quake) |
| MDL | Model file element (Rational Rose) |
| MDM | Modem definition (Telix) |
| MDN | Blank database template (Microsoft Access) |
| MDT | Data table (Microsoft ILink incremental linker) |
| MDT | Add-in file (Data) (Microsoft Access) |
| MDW | Workgroup (Microsoft Access) |
| MDX | Multiple index file (dBase IV) |
| MDZ | Wizard template (Microsoft Access) |
| ME | ASCII text document (Generic) |
| MEB | Macro editor bottom overflow library (Microsoft WordPerfect for Windows) |
| MED | Music module (MOD) (OctaMed Music Editor) |
| MED | Macro editor delete save file (Microsoft WordPerfect for Windows) |
| MEM | Macro editor macro (Microsoft WordPerfect for Windows) |
| MEM | Memory variable save file (Clipper) |
| MEM | Memory variable save file (dBase IV) |
| MEM | Memory variable save file (Microsoft FoxPro) |
| MEQ | Macro editor print queue file (Microsoft WordPerfect for Windows Library) |
| MER | Format for interchanging spreadsheet/database data; recognized by Filemaker, Excel, and others |
| MER | Macro editor resident area (Microsoft WordPerfect for Windows Library) |
| MES | Macro editor workspace file (Microsoft WordPerfect for Windows) |
| MES | Message file (Generic) |
| MET | Presentation Manager metafile |
| MET | Macro editor top overflow file (Microsoft WordPerfect for Windows Library) |
| MET | Document file (OmniPage Pro) |
| MEU | Menu group (DOS Shell) |
| MEX | Executable command (Matlab) |
| MEX | Macro editor expound file (Microsoft WordPerfect for Windows) |
| MF | Metafont text file |
| MFG | Manufacturing file (Pro/ENGINEER) |
| MGF | Font file (MicroGrafx) |
| MGF | A file in a Materials and Geometry Format |
| MHP | Internet mail document (Mailshift) |
| MHT | MHTML document (Microsoft) |
| MHTM | MHTML document (MIME) |
| MHTML | MHTML document (MIME) |
| MI | Data file (Cocreate ME10) |
| MI | Miscellaneous file (Generic) |
| MIC | Image Composer file (Microsoft) |
| MID | MIDI music |
| MIF | Interchange format (Adobe FramMaker) |
| MIFF | Machine Independent File (Generic) |
| MII | Datafile (MicroStat-II) |
| MIM | A multipart file in the Multi-Purpose Internet Mail Extensions (MIME) format; often created as the result of sending e-mail with attachments in AOL. The files in a multipart MIM file can be "opened" (unarchived and separated into individual files) using Winzip or a similar program. |
| MIME | See MIM. |
| MIX | Object file (Power C) |
| MIX | Picture file (Microsoft PhotoDraw 2000) |
| MIX | Picture file (Microsoft Picture-It!) |
| MIX | Package file (Command & Conquer) |
| MIX | Resource archive (Westwood Studios) |
| MJF | Audio file similar to MP3 (Mjuice) (Opens with WinAmp) |
| MK | Makefile (Generic) |
| MKE | Makefile (Microsoft Windows SDK) |
| MKI | Graphic Image (MagView 5.0) (Japanese) |
| MKS | Datafile (TACT) |
| ML3 | Project file (Milestones 3.x) |
| MLB | Macro library (Symphony) |
| MLI | A file in 3D Studio's Material-Library format |
| MLID | Muliple link interface driver file (Generic) |
| MLM | Groupwise email file (Novell Groupwise) |
| MM | Text file (MultiMate Advantage II) |
| MMC | Catalog file (Microsoft Clip Gallery 5.x) |
| MMF | Mail message file (Microsoft Mail) |
| MME | A multipart file in the Multi-Purpose Internet Mail Extensions (MIME) format; often created as the result of sending e-mail with attachments in AOL. The files in a multipart MME file can be "opened" (unarchived and separated into individual files) using Winzip or a similar program. |
| MMF | Meal Master Format, a recipe catologing format |
| MMF | Mail file (Microsoft) |
| MMG | Beyond 20/20 table or aggregate data file |
| MML | Bulk mail file (Created by MyMailList) |
| MMM | Multimedia movie (Microsoft) |
| MMM | Multimedia movie (MacroMind Director 3.x) |
| MMO | Memo Writer file (RapidFile) |
| MMP | MindManager file (MindMapor) |
| MMP | Output video (Bravado) |
| MN2 | Mission file (Descent2) |
| MN3 | Mission file (Descent3) |
| MND | Menu source (AutoCAD Menu Compiler) |
| MND, MNI | Mandelbrot for Windows |
| MNG | Map (DeLorme Map'n'Go) |
| MNG | Multi-image Network Graphics |
| MNT | Menu file (Microsoft FoxPro) |
| MNU | Menu file (Visual dBase) |
| MNU | Advanced macro (HP NewWave) |
| MNU | Interact menu (Intertal Systems) |
| MNU | Menu (AutoCAD Menu Compiler) |
| MNU | Menu (Norton Commander) |
| MNX | Menu (Microsoft FoxPro) |
| MNX | Compiled menu (AutoCAD) |
| MNY | Account book (Microsoft Money) |
| MOB | Device definition (PEN for Windows) |
| MOD | FastTracker, StarTrekker, Noise Tracker (etc.) music module file |
| MOD | Spreadsheet (Microsoft Multiplan) |
| MOD | Modula-2 source code file (Clarion Modula-2) |
| MOD | Kernel module (Microsoft Windows 9.x) |
| MOD | Amiga/PC tracker module |
| MON | Monitor description (ReadMail) |
| MOV | Movie (QuickTime for Microsoft Windows) |
| MOV | Movie (AutoCAD/AutoFlix) |
| MOZ | Zipped (Compressed) mod file |
| MP2 | MPEG Audio Layer 2 |
| MP3 | MPEG Audio Layer 3 (AC3) |
| MPA | MPEG-related file (MIME type 'mpeg') |
| MPC | Calendar file (Microsoft Project) |
| MPD | Database file (Microsoft Project) |
| MPE | MPEG animation |
| MPEG | MPEG animation |
| MPG | MPEG animation |
| MPM | Mathplan Macro library (Microsoft WordPerfect for Windows) |
| MPP | Project file (Microsoft Project) |
| MPP | Drawing file (CAD) |
| MPR | Menus (compiled) (Microsoft FoxPro) |
| MPT | Bitmap graphics (Multipage TIFF) |
| MPV | View file (Microsoft Project) |
| MPX | Compiled menu program (Microsoft FoxPro) |
| MPX | Exchange file (Microsoft Project) used for exporting data |
| MP2 | MPEG Audio Layer 2 file (MIME video file) |
| MP3 | MPEG Audio Layer 3 (AC3) file |
| MRB | Multiple resolution bitmap graphics (Microsoft C/C++) |
| MRI | MRI Scan |
| MRS | Macro resource file (Microsoft WordPerfect for Windows) |
| MSA | Archive (Magic Shadow) |
| MSC | Makefile (Microsoft C) |
| MSC | Common console document (Microsoft Windows 2000) |
| MSD | Diagnostics report file (Microsoft MSD) (Diagnostics) |
| MSDL | Scene Description Language (Manchester) |
| MSG | Mail message (Microsoft) |
| MSI | Installer package (Microsoft Windows) |
| MSN | Network document (Microsoft) |
| MSN | Mission File (Descent) |
| MSP | Paint bitmap (Microsoft) |
| MSP | Windows Installer patch file |
| MSS | Manuscript text file (Perfect Writer) |
| MSS | Manuscript text file (Scribble) |
| MSS | Manuscript text file (MINCE) |
| MSS | Manuscript text file (Jove) |
| MST | Windows Installer transform |
| MST | Minispecification file (Prosa) |
| MST | Setup script (Microsoft SDK) |
| MSW | Text file (Microsoft Word) |
| MSX | Compressed CP/M archive (MSX) |
| MTH | Math file (Derive) |
| MTM | Music module (MOD) (Multitracker) |
| MTW | Datafile (Minitab) |
| MTX | Twain device driver (32 bit)(UMax) |
| MU | Menu (Quattro Pro) |
| MUL | Online game called Ultima online |
| MUS | Music (Generic) |
| MUS | Interactive music audio data file (Electronic Arts) |
| MUS | Music (MusicTime) |
| MUS10 | Audio (Mus10) |
| MV | Server-side script file (Miva) |
| MVA | Video accelerator file (Matrox) |
| MVB | Multimedia Viewer file (Microsoft) |
| MVC | Image file (Sony Digital Mavica) |
| MVE | Interplay video file (Descent2, Fallout2) |
| MVF | Stop frame file (AutoCAD-AutoFlix) |
| MVI | Movie command file (AutoCAD-AutoFlix) |
| MVW | Log file (Saber LAN) |
| MWF | Animation (ProMotion) |
| MWP | Smartmaster file (Lotus WordPro 97) |
| MXD | Map file (ArcInfo) |
| MXT | Datafile (Microsoft C) |
| MYP | Presentation file (Make Your Point) |
2010 Liberty Boy
Le Havre