# What is a DMG file?

> A DMG is a disk image, a single file that opens like a drive. Learn how apps ship in one, how to install from it and how to verify the download.

Canonical: https://www.notchstar.com/glossary/dmg/
Last updated: 2026-11-04

Published 2026-11-04.

A DMG is a disk image: one file that macOS opens like a small drive. Many Mac apps are downloaded as a DMG, and the app you want sits inside it.

## Why it matters

Installing from a disk image has two steps: open the file, then copy the app out. Apple's help page for installing apps says to double click the disk image or package file. Once the app is in your Applications folder, you can eject the disk image and delete the download.

## How to install NotchStar

The install page gives three steps. Download the disk image, open it, and drag NotchStar to Applications. Then open NotchStar from Applications. The star appears in your menu bar and the notch is ready.

## Verify the download

The install page lists a SHA256 checksum for the file. You can compute yours in Terminal with `shasum -a 256 ~/Downloads/NotchStar-1.0.5.dmg` and compare. If the two strings match, the file is the one published. The disk image and the app inside it are [notarized](https://www.notchstar.com/glossary/notarization/) by Apple, with the ticket attached to both, so [Gatekeeper](https://www.notchstar.com/glossary/gatekeeper/) can check them.

## Updating

Version 1.0 has no automatic updater. Download the new version from the site and drag it over the old one. Your settings and license carry over.

## Related

Read [is NotchStar safe](https://www.notchstar.com/guides/is-notchstar-safe/) for what to check after install. The tool you will see first is the [Clipboard](https://www.notchstar.com/features/clipboard/).

## Keep reading.

- [What is notarization on Mac?](https://www.notchstar.com/glossary/notarization/): Notarization is Apple's automated check of Mac software before you download it. Learn what Apple says it covers and what it does not.
- [What is Gatekeeper on a Mac?](https://www.notchstar.com/glossary/gatekeeper/): Gatekeeper is the macOS check that decides whether downloaded software may run. Learn what it checks, why it shows warnings and how it relates to notarization.
- [Is NotchStar safe? Signing, permissions and what it sends](https://www.notchstar.com/guides/is-notchstar-safe/): NotchStar is signed and notarized by Apple, needs no account and sends nothing unless you opt in. See every permission it asks for and how to check it yourself.
- [Clipboard history that lives in your notch](https://www.notchstar.com/features/clipboard/): Searchable clipboard history in the Mac notch: text, links, images and files. Skips password manager copies. Click any item to copy it again.

## More in Security and signing.

- [What is Gatekeeper on a Mac?](https://www.notchstar.com/glossary/gatekeeper/): Gatekeeper is the macOS check that decides whether downloaded software may run. Learn what it checks, why it shows warnings and how it relates to notarization.
- [What is notarization on Mac?](https://www.notchstar.com/glossary/notarization/): Notarization is Apple's automated check of Mac software before you download it. Learn what Apple says it covers and what it does not.
- [What is an Apple Developer ID?](https://www.notchstar.com/glossary/developer-id/): A Developer ID is the certificate Apple gives developers to sign Mac apps shared outside the App Store. Learn what it proves and what it does not.
- [What is the hardened runtime?](https://www.notchstar.com/glossary/hardened-runtime/): The hardened runtime is a code signing setting that limits what a Mac app can do. Learn what it blocks and how entitlements relax it.
- [What are entitlements in macOS?](https://www.notchstar.com/glossary/entitlements/): Entitlements are key value pairs signed into a Mac app that grant it permission to use a service or technology. Learn what NotchStar asks for and why.
- [What is the App Sandbox on Mac?](https://www.notchstar.com/glossary/app-sandbox/): The App Sandbox is a macOS feature that limits an app's access to system resources and user data. Learn how it differs from the hardened runtime.