How to Install a Mac App from a DMG File

A .dmg file is not an app and it is not an installer. It's a disk image — a sealed container that macOS can mount like a USB stick. Installing the app inside it means copying that app out of the container and into your Applications folder, then throwing the container away. Here's how it works.

The short version

Double-click the .dmg to mount it.
Drag the app onto the Applications folder.
Eject the mounted disk image.
Open the app and click Open at the security prompt.
Move the .dmg to the Trash.

Step 1 — Open the disk image

Find the downloaded file (usually in ~/Downloads) and double-click it. macOS mounts the image and it appears in the Finder sidebar under Locations, alongside your real drives. A window opens showing what's inside.

Nothing has been installed at this point. The app is sitting on a read-only virtual disk, and if you launch it from there it may behave strangely or refuse to update itself. Copy it out first.

Step 2 — Drag the app to Applications

Most DMG windows show two things: the app icon and a shortcut to your Applications folder, often with an arrow between them. Drag the app onto that shortcut.

If the window has no Applications shortcut, drag the app to Applications in the Finder sidebar instead, or press Command-C on the app and paste it into a Finder window pointed at /Applications.

This is a copy, not a move — the original stays on the disk image. Large apps take a moment, so wait for the progress bar to finish before moving on.

Step 3 — Eject the disk image

The mounted volume stays attached until you eject it. Click the eject arrow next to it in the Finder sidebar, or select it and press Command-E.

If macOS says the disk is in use, the app is probably still running from the image, or a Finder window is still open inside it. Quit the app, close the window, and try again.

Step 4 — Open the app for the first time

Anything you download through a browser gets tagged by macOS with a quarantine flag. The first time you launch it, you'll see a dialog saying the app was downloaded from the internet and asking whether you're sure. Click Open. You only see this once per app.

If instead you get "macOS cannot verify that this app is free of malware" or "the developer cannot be verified", the app isn't notarized by Apple. On recent versions of macOS you can't dismiss that from the dialog — you have to open System Settings → Privacy & Security, scroll down, and click Open Anyway. Only do that if you trust where the app came from.

Step 5 — Delete the DMG

Once the app is in Applications and opens correctly, the disk image has done its job. Drag the .dmg to the Trash. If you don't, your Downloads folder quietly fills up with installers you'll never open again — see what to do with a DMG file after installing for the details.

When the DMG doesn't follow the script

Not every disk image is a simple drag-and-drop. The common variations:

It contains a .pkg file. That's an Apple installer package, not an app bundle. Double-click it and follow the installer — don't drag it to Applications.
A license agreement appears before it mounts. Some images carry a software licence agreement that macOS makes you accept first. Read it or don't, but you have to agree before the volume appears.
It contains several apps. Usually the main app plus an uninstaller or helper. Only copy the one you actually want.
It asks for a password. The image is encrypted. You need the passphrase from whoever sent it; macOS can't recover it.
"The application is damaged and can't be opened." Usually a broken or missing code signature, or an incomplete download. Re-download from the developer's official site before trying anything more drastic.

The one-double-click version

Every step above is mechanical, which is exactly the kind of thing a computer should be doing for you. EasyDMG replaces DiskImageMounter as your handler for .dmg files, so a double-click does the whole sequence: mount the image, run the same Gatekeeper security check macOS runs, copy the app into Applications, open it (or reveal it in Finder), unmount the image, and — if you've turned that on — move the DMG to the Trash.

It's deliberately conservative about the edge cases above. A package installer, a licence agreement, an ambiguous multi-app image, or a bundle that doesn't validate all cause it to stop, mount the image, and hand the job back to you rather than guess.

Stop dragging icons. EasyDMG is free, open source, signed and notarized, and runs on macOS 13 or later.

Download EasyDMG