If you’re a macOS user, chances are you’ve come across PKG and DMG files at some point. Both are common filename extensions used for various file formats, but there are some basic differences you should be aware of.
What is PKG?
The PKG file format is commonly used by Apple on its mobile and computing devices. It is supported by macOS and iOS and includes software packages from Apple. This is not exclusive to Apple devices, as Sony also uses PKG to install software packages on PlayStation devices.
The contents of the PKG file format can be extracted and installed using Apple Installer. It is very similar to a compressed file; you can right-click the file to view the contents, and files are compressed when compressed.
The PKG file format maintains an index to the data block to read each file inside. The PKG filename extension has been around for quite some time and has been used in Apple Newton operating systems, as well as Solaris, an operating system currently maintained by Oracle. Additionally, legacy operating systems like BeOS also used PKG files.
PKG files contain instructions on where to move certain files when installed. It uses these instructions when extracting, copying the data to specific locations on the hard drive.
What is a DMG file?
Most macOS users are familiar with the DMG file format, short for Disk Image File. DMG is the Apple Disk Image file extension. It is a disk image that can be used to distribute software or other files and can even be used for storage (like removable media). Once mounted, it replicates removable media, such as a USB key. You can access the DMG file from your desktop.
DMG files usually move files to the Applications folder. You can create DMG files using Disk Utility, which is also available with macOS Ventura.
These are usually raw disk images containing metadata. Users can also encrypt DMG files if needed. Think of them as files containing everything you expect on a disc.
Apple uses this format to compress and store software installation packages instead of physical discs. If you’ve downloaded software for your Mac from the web, you’ve probably come across DMG files.
Key Differences Between PKG and DMG Files
Although they may look similar and can sometimes perform the same functions, there are key differences between PKG and DMG files.
Folder vs Image
Technically, PKG files are usually folders; they bundle multiple files into one that you can download together. PKG files are installation packages. DMG files, on the other hand, are simple disk images.
When you open a DMG file, it launches the software installer or the content stored in it, often appearing as a removable drive on your computer. Remember that DMG is not an installer; it’s just a removable media image, like an ISO file.
General archive openers on Windows can be used to open PKG files. You can also open DMG files in Windows, although the process is slightly different.
PKG files may include post-installation or pre-installation scripts, which may include instructions on where to install the files. It can also copy multiple files to one location or install files to multiple locations.
DMG files install software in main folders. The file appears on the desktop and the content is usually installed in Applications.
DMGs can support relative paths to populate existing users (FEU), making it easier for developers to include how-to guides, such as conventional ReadMe documents, for every user on the system.
Technically, you can also add such files to PKG, but this requires significant expertise and experience with post-installation scripts.
DMG and PKG files serve different purposes
Although both are commonly used, their purpose is a bit different. DMG files are much more flexible and suitable for distribution, while PKG files offer greater options for specific installation instructions. Additionally, they are both compressed, reducing the size of the original file.