File Types

iMatt mini

macrumors 6502
Original poster
Mar 1, 2005
Central New Jersey
Coming from a Windows life, what file types are different?
It looks like DMG=EXE but I'm not even sure on that.
I've never used Mac's to the extent of looking at file types, just basic web browsing and iTunes and Photoshop.


Moderator emeritus
Jul 24, 2002
A DMG is a disk image. It's like a filesystem contained in a single file. It is not executable (it's a bit like a .iso).


Moderator emeritus
Oct 21, 2003
Portland, OR
I think most file extensions are about the same, assuming the applications that create them exist on both computers. There are a few that don't exists on Windows, .dmg being one of them. I suspect .pkg and .mpkg don't exist (or aren't the same) on Winodws. It's a package file that contains OS X installers (and the associated peices/parts).

But really, this is just too expansive a question to answer. :)

Doctor Q

Staff member
Sep 19, 2002
Los Angeles
The equivalent of a Windows .exe file is called .app (for "application") under Mac OS X, although file extensions aren't always displayed. An .app file is actually a packaged collection of files, containing the run-time code and various resource files, but you don't have to be aware of that since Mac OS X makes it look like a single application file unless you specifically ask to see the contents.

Years ago, Mac files included within them a "creator" tag that identified what application they belonged to, so Mac OS knew what program to launch from the file's content, not the filename. But Mac OS X now relies by default on knowing what application to launch based on a file's extension, as Windows does.

Extensions such as .txt (text), .pdf (Acrobat file), and .doc and .xls (MS Office) are the same as Windows. Extensions for the main types of executable files are different. In addition to .app for executable applications, for example, there are executable .scpt files (one of the ways to store AppleScript files), and executable .command files (Unix-style shell scripts). There is also .workflow, an executable script created with the Mac OS X "Automator" application. Some executables, such as perl programs, can use the same extensions as under other operating systems.
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