FastDMG For Mac

Disk image verification tells you if a .dmg file has been corrupted after creation. This can be helpful, but it is also time-consuming, particularly for very large files. All images you mount are verified automatically on macOS, and waiting for these checks can waste valuable time.

FastDMG is an open-source app that acts as a replacement to DiskImageMounter, the default macOS app for handling disk images. It is a GUI for Apple's hdiutil command-line utility, and it allows you to skip both verifications and user license agreements. It runs in the background, just like DiskImageMounter.

First off, you need to move the app to your Applications folder. Next, launch it and configure it to your taste. Then, right-click a .dmg file and click Get Info (alternatively, click it and press ⌘I). Finally, select FastDMG from the Open with dropdown, and click Change All.

All DMG files will now be opened with FastDMG. The app can also handle .iso and .toast images, and you can follow the same steps to change the default app for these files as well.

You might not notice much of a difference if you have a recent Mac and open a small .dmg file, but the benefit is very noticeable when working with an older system or mounting a large disk image.

FastDMG also accepts all user license agreements automatically, which some developers choose to add to their .dmg files. This won't make much of a difference for regular users, but if you need to mount dozens of images on a daily basis, it's a welcome aid.

After configuring the app for the first time, you'll never have to see it again. It runs in the background, and it feels like you're using Apple's default disk image mounter. The only difference is that it's faster.

Since it uses hdiutil to open files, a command-line tool included in macOS, FastDMG is as dependable as you can expect. The project is also open-source, so you can check out the code if you're curious about how it works.