Can I delete the .dmg files on my Mac once I install the app?

Question

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.

Answer 1

Yes.

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.

Answer 2

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

Answer 3

I would say that you can but you may find keeping some or all may save you a lot of aggro one day. Last year I had a problem with my - under guarantee- iMac. It had to be reset to zero with a complete reinstall. Then my old MacBook Air had a major problem and I replaced it with a new MBA. In both cases I lost all my applications. I was using an old version of Filemaker Pro. And FM now no longer allow downloads of the .dmg. Only backups. I was very glad that I kept the original .dmg (400mb). I had kept the dmgs of my important applications and reinstalling them was made much easier. Perhaps you have a dozen of dmgs. So store them on a USB KEY. or even a sd camera type card. 16gb or 32gb is plenty large enough. You will thank me one day.