This page provides a list of those file extensions that start with .m. The information given below is a summary and further details can be found by clocking on the summary next to the file extension of interest.

.m1vMPEG movie.
.m2tsSony high definition video file.
.m3uMP3 play list.
.m4aApple Inc MPEG 4 file.
.m4riPhone ringtone file.
.mapLinker map file | MapInfo file | Manifold project file.
.maqAccess query.
.marAccess report.
.marcMachine Readable Cataloging file.
.matMaterial file.
.maxPaperPort image file.
.mbMapBasic source file.
.mbmMultiBitMap file.
.mbsOpera mailbox | Multi bit series file | Master Bibliography style file | MR Tech Zip backup | Macrografx Picture Publisher Brush | Mailbag assistant script.
.mbxMapBasic application file | Eudora Mailbox file | Outlook Express Mailbox file.
.mcdMotion capture plugin (Animation Master).
.mcoMSN messenger winks file | XtraMusic file (tentative).
.md5Shorten audio checksum file | MD5 checksum file.
.mdaMicroDesign area file.
.mdbAccess database.
.mdeAccess database (compiled).
.mdfSQL Server database file | CD image file.
.mdiMicrosoft Document Imaging image file.
.mdlRose model file | Animation Master model file.
.mdmpWindows Minidump file.
.mdpMicroDesign page file.
.mdsCD image file.
.mdxMapServer database index file | dBase index file.
.mglMascopt network graph file | plvdkey management summary file.
.mhtWeb archive file.
.mhtmlModular Hyper Text Mark-up Language web page | Web archive file.
.midMIDI file | MapInfo interchange file.
.mifMapInfo interchange file.
.mimA MIME file.
.mixPower C object file | Command and Conquer file | PhotoDraw picture | Picture IT! picture | Dance eJay music mix.
.mkvMatroska video file.
.mmFreeMind mind map file | Matrix Market file.
.mmaMusical MIDI Accompaniment song file | Master Album Maker Album.
.mmapMindManager mind-map file.
.mmdMail Message Download file
.mn2Descent 2 mission file.
.modWindows kernel module.
.moddPicture Motion Browser data file.
.moffPicture Motion Browser index file.
.motMotion file.
.movQuckTime movie.
.movieSilicon Graphics movie.
.mozNetscape cache file.
.mp2MPEG 2 audio file.
.mp3MPEG 3 audio file.
.mp4MPEG 4 audio file.
.mpcMusepack (audio) file.
.mpeMPEG movie.
.mpegMPEG movie.
.mpgMPEG movie.
.mppMicrosoft Project file | CAD drawing file.
.mptMicrosoft Project template file.
.mrcMachine readable cataloging file | mIRC script | Medical Research Council (3D) image file.
.mscMMC snap-in file | CRiSP fish stocks file.
.msdvdWindows DVD Maker project file.
.mseMSwinEHE project file.
.msfThunderbird Mail Summary file | Miranda IM skin file.
.msgOutlook message file | Fidonet message.
.msiSystem installer package.
.msmSystem installer merge module.
.msnDescent 1 mission file.
.mspMicrosoft System Installer Patch file | Midi Studio Project file.
.mspxASP.NET file.
.mstMicrosoft System Installer Transform file
.msvMemory Stick Voice file | MyStars saved file.
.muiWindows Multilingual resource file | Amega Magic User Interface file.
.mvlDescent 2 movie archive.
.mwsMapInfo workspace file.
.mxdArcGIS map document file.
.mxmlAdobe Flex interface markup file.
.mxtArcGIS map template file.
.mydMySQL data file | MyDefrag script.
.myiMySQL index file.

For further information about the file extension please do click on the summary next to the file extension in the list above.

We would like this listing to be complete and comprehensive, but recognised that we may have missed one and that new file types are being used all the time. So if you know of a file type that we have missed that should be listed here then please let us know.