The common practice is for the app developers to provide an
uninstall-xyz.pkg, especially if the app installs some privileged helpers or other files outside of its
If there are no uninstall packages or scripts provided by the app developer, then you can unpack the pkg file and see what's inside it. An easier alternative is to use an app that can peek inside a
.pkg and show you what files are copied where and what pre- and post-install scripts are run. This can be done for example with SuspiciousPackage (freeware) or Pacifist (nagware).
With SuspiciousPackage pressing Space (or QuickView) in Finder on a
.pkg file will show something like this:
From this screen you can further navigate to inspect the files in the package as well as the
Additionally, Pacifist has an option to Analyze Existing Installations which will let you inspect what a package had installed even if you don't have the original
.pkg at hand.