.pkg

What is a .pkg file?

PKG is the standard macOS installer format — distributing apps, system extensions, drivers, and other components.

Use caution
Type System
By Apple
MIME application/x-newton-compatible-pkg

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What is it

You downloaded software for your Mac and it came as a .pkg file. Unlike DMGs (which are just disk images containing an app you drag to Applications), PKG files are actual installers — they can write files to system directories, install kernel extensions, run pre- and post-install scripts, and modify system configuration.

PKG files use Apple's Installer framework and can contain multiple packages (a "distribution" package). They're used for software that needs to install components outside the Applications folder — system extensions, drivers, command-line tools, launch daemons, and preference panes. macOS Gatekeeper checks PKG signatures and will warn you about unsigned or unnotarised packages.

macOS runs PKG files natively through Installer.app (double-click to start). Suspicious Package (free, macOS) lets you inspect the contents of a PKG without installing — see every file it will write and every script it will run. Use it for packages from unfamiliar sources. Terminal alternative: `pkgutil --expand package.pkg /tmp/expanded` to extract and inspect.

Technical details
Full Name
macOS Installer Package
MIME Type
application/x-newton-compatible-pkg
Developer
Apple
Magic Bytes
N/A
Safety
.pkg requires caution. PKG files install software and can run scripts with elevated permissions. Only install from trusted developers.
What opens it
macOS Installer (runs natively)
FREE macOS
Suspicious Package (inspect)
FREE macOS
FAQ
What's the difference between DMG and PKG?
DMG is a disk image — usually contains an app you drag to Applications. PKG is an installer that can write files to system directories, run scripts, and install system components. DMGs are simpler; PKGs are more powerful and potentially riskier.
How do I inspect a PKG before installing?
Download Suspicious Package (free, mothersruin.com) — it shows every file the PKG will install and every script it will run. Alternatively: `pkgutil --expand package.pkg /tmp/inspect` then browse the extracted contents.
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