How to create a DMG installer for an applications on macOS?

Creating a DMG (Disk Image) installer for an application on macOS is a common way to distribute software in a user-friendly format. Below are the steps to create a DMG installer for your application:

This video describes the process carefully:

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Steps to Create a DMG Installer on macOS:

1. Prepare Your Application

• Ensure your application is fully built and functional (e.g., compiled into a .app bundle).
• Place the .app file in a folder (e.g., name it MyAppInstaller) along with any additional files you want to include (like a README, license file, or scripts).

2. Create a Disk Image

• Open Disk Utility (found in Applications > Utilities or via Spotlight).
• Go to the menu: File > New Image > Blank Image.
• Configure the settings in the dialog box:
  • Save As: Name your DMG (e.g., MyAppInstaller.dmg).
  • Where: Choose a location to save the DMG (e.g., Desktop).
  • Name: Give the mounted volume a name (e.g., MyApp).
  • Size: Set a size large enough to hold your app and extra space for aesthetics (e.g., 50MB or more, depending on your app size).
  • Format: Choose Mac OS Extended (Journaled).
  • Encryption: Select none (unless you want a password-protected DMG).
  • Partitions: Select Single partition - GUID Partition Map.
  • Image Format: Choose read/write disk image.
• Click Save. This creates a blank DMG file.

3. Mount and Customize the Disk Image

• Double-click the newly created .dmg file to mount it. A new volume (e.g., MyApp) will appear on your Desktop or in Finder.
• Copy your .app file (and any additional files) into the mounted volume.
• Optionally, add a background image or customize the appearance:
  • Create a background image (e.g., 560×400 pixels, PNG format) with instructions like “Drag to Applications”.
  • Place the image in the mounted volume.
  • In Finder, right-click in the volume, select Show View Options, and:
  • Set the background to your image (drag it into the “Picture” section).
  • Adjust icon size (e.g., 64×64 or 128×128).
  • Arrange the .app file and other items neatly.
• Add a shortcut to the Applications folder:
  • In Finder, press Command + T to open a new tab, navigate to /Applications, and drag the Applications folder into the DMG volume while holding Option + Command to create an alias.

4. Eject and Finalize the DMG

• Eject the mounted volume by dragging it to the Trash (or right-click and select Eject).
• Convert the read/write DMG to a compressed, read-only version:
  • Open Disk Utility again.
  • Go to File > New Image > Image from Folder.
  • Select the folder containing your .app (or the mounted DMG content if you prefer), and click Choose.
  • In the dialog:
  • Save As: Name the final DMG (e.g., MyAppInstaller-final.dmg).
  • Where: Choose a save location.
  • Image Format: Select compressed.
  • Encryption: Choose none (or add encryption if desired).
  • Click Save. Disk Utility will create a compressed .dmg file.

5. Test the DMG

• Double-click the final .dmg file to mount it.
• Verify that it looks as intended (e.g., background image, layout) and that dragging the .app to the Applications alias works.
• Test the application after installation to ensure it runs correctly.

6. Distribute the DMG

• Share the finalized .dmg file with users via a website, email, or other means.
• Optionally, sign the DMG with a Developer ID for Gatekeeper compatibility:
  • Use the codesign command in Terminal:
    codesign -f -s "Developer ID" MyAppInstaller-final.dmg
  • Replace "Developer ID" with your actual Developer ID certificate name (viewable in Keychain Access).

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Optional Enhancements

• Notarization: If distributing publicly, notarize your app and DMG with Apple to avoid Gatekeeper warnings:
• Use xcrun altool or Xcode to submit the DMG for notarization.