---
id: mac-storage-basics.what-are-disk-images-and-sparse-bundles
url: https://storagestudio.us/faq/mac-storage-basics/what-are-disk-images-and-sparse-bundles
category: "Mac storage basics"
subcategory: "Disks, APFS and formats"
question: "What are disk images (.dmg) and sparse bundles?"
alt_questions:
  - "what is a sparsebundle"
  - "dmg vs sparseimage"
  - "disk image taking space mac"
  - "create disk image mac"
  - "sparse bundle size"
short_answer: "A disk image is a file that acts like a drive. A .dmg has fixed contents; sparse images and bundles grow as you add files and need compacting to shrink."
tags: ["disk image", "dmg", "sparse bundle"]
related: ["https://storagestudio.us/faq/mac-storage-basics/can-i-delete-dmg-files-after-installing"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# What are disk images (.dmg) and sparse bundles?

A **disk image** is a file that behaves like a drive when you open it. A **.dmg** has a fixed contents size and is how most apps are distributed. A **sparse image** or **sparse bundle** grows as you add files (a sparse bundle stores itself as many small pieces, which suits backups and syncing).

You can make one in **Disk Utility → File → New Image**. Sparse images don't automatically shrink when you delete files inside; Disk Utility's Resize or the `hdiutil compact` command reclaims the space.