Pkg Viewer -

: If you need to access internal files, right-click the file list and select Extract All or specific folders to your desktop. Alternative: macOS PKG Files

: Checks if a package is a "Fake PKG" (fPKG) or an official retail package. PKG Viewer

If you are referring to standard Apple installer files, you do not need a special "viewer" app. You can use the built-in option in the macOS installer to see what will be installed before you run it. Alternatively, the command-line tool pkgutil --expand file.pkg output_folder can be used to unpack them. : If you need to access internal files,