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Disk images (.dmg)

Purrchiver opens, extracts, and creates .dmg disk images — you can treat one like any other archive. You can also still mount a DMG in Finder the classic way; this page covers both.

What a DMG is

A DMG (UDIF — Universal Disk Image Format) is a file that contains a complete filesystem image — what you’d see if you formatted a disk and copied files onto it. macOS treats them like virtual disks: when you double-click one, the system mounts it as if you plugged in a USB drive. The contents show up in Finder as a mounted volume you can browse and drag from.

Apps you download from the web on macOS usually come as DMGs. You mount the DMG, drag the app to /Applications, unmount the DMG. It’s the standard distribution method outside the App Store.

Opening a DMG in Purrchiver

Drag a .dmg onto Purrchiver (or use File → Open Archive…) and it lists the contents like any archive — no mounting required. From there you can extract everything, pull out a single item, or drag entries straight to Finder. Encrypted DMGs prompt for the password first, the same as any encrypted archive.

This is handy when you just want a file or two out of a DMG without mounting it as a volume and ejecting it afterward.

Creating a DMG

Pick DMG in the Create Archive sheet to bundle a selection into a disk image. A plain (unencrypted) DMG is free to create; an encrypted (AES-256) DMG is part of the one-time $9.99 unlock. Purrchiver builds it via Apple’s own hdiutil, sandbox-safe and without mounting anything during creation. The result double-clicks open in Finder like any other DMG.

Mounting a DMG in Finder instead

You don’t have to use Purrchiver — the classic path still works:

Double-click in Finder. The DMG mounts as a volume on your Desktop / in Finder’s sidebar. Browse it, drag what you need out, then eject it:

  • Drag the volume to Trash, or
  • Select the volume and press ⌘E, or
  • Right-click the volume → Eject

If double-click doesn’t work — usually because the DMG file is corrupt or was downloaded incompletely — open Disk Utility (in Applications → Utilities) and use File → Open Disk Image… to inspect what’s wrong.

What about .iso?

.iso files are a different beast. There are two cases:

  1. Bootable ISOs (Linux distro install media, etc.) — macOS mounts these natively, just like DMGs. Double-click in Finder.
  2. Data ISOs (data discs, archived CD/DVD content) — Purrchiver does read these, treating them as ISO 9660 archives. Drag onto Purrchiver to extract.

If you’re not sure which one you have, try Purrchiver first. If the file is a data ISO, you’ll see the contents listed; if Purrchiver can’t open it, it’s most likely a bootable ISO — try Finder.