An installer should be filename.pkg (installer package) or filename.mpkg (multi-package – 2 or more packages that typically run in series). In Windows, they both look the same (filename.exe), but in OS X, an app SHOULD be a ready to use bundle. One comment mentions distinguishing an installer from an app. It is possible for a Zip to be programmed to self-expand and the contents can be programmed to self-install. There is a level of verification that does not occur with a Zip. There is also some increased security process for DMG. These folks who put an arrow image in their DMG window should add the words 'DRAG TO APPLICATIONS' to the arrow, because I promise you, a surprising percentage of new-to-Mac folks miss the idea, as one commenter here said. DMG works similar to connecting a thumb drive – no startup volume space is needed, until you drag the needed files to the internal drive. Zip needs drive space to expand, since it actually makes a new directory to duplicate in larger format what is in the archive.

Zip files for mac