I have recently noticed that my 8-year-old MacBook is slow when loading webpages, and I started going through my files to get rid of old stuff. After a while, I came across a file called "discord.dmg". I think this was the file used to install Discord on my computer, but now I am wondering if I can delete the .dmg without getting rid of the application.



You can safely delete .dmg files.

A disk image file (.dmg) is simply an easy, portable structure to transfer an app to you without falling afoul of any internet 'oddities' such as compression, splitting etc. So long as the .dmg arrives intact [& it is self-checking in this regard] then you can be sure it arrived "as sent" & can copy it to your Applications folder. Once you have done that, the .dmg itself is no longer required & can just be deleted.

The only two reasons to keep them would be for:

  1. archival purposes - just in case the original becomes unavailable for any reason & you might one day need to reinstall on a new Mac (if you have it backed up to Time Machine you can delete it sooner of course).
  2. Incomplete installation - some people run apps out of a DMG and don’t install the app drag and drop. In this case, put the dmg in the trash but don’t empty it. Reboot and if you can run the app, it’s safe to empty the trash.
  • Does this also apply to .pkg files? – Oskar May 11 '20 at 17:45
  • Essentially, yes. .pkg files are usually needed if the installer needs to do other "work", putting files inside the system. Many [but not all] .dmg files require only that you copy the app to applications. the difference isn't important other than that. Both can be discarded after use. – Tetsujin May 11 '20 at 17:54

Yes you should trash it if you have loaded the software. Its done its job and is only taking up disk space now.

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