GeezerVison

.pkg (package) is a filename extension used for several file formats that contain packages of software and other files to be installed onto a certain device, operating system, or filesystem, such as macOS, iOS, the PlayStation Vita, the PlayStation 3, the PlayStation 4 and the PlayStation 5.

• macOS and iOS use .pkg extensions for Apple software packages using the Xar format internally.
• PlayStation Vita, PlayStation 3, PlayStation 4, PlayStation 5 – used for installation of PlayStation Vita, PlayStation 3, PlayStation 4 and PlayStation 5 software, applications, homebrew, and DLC from the PlayStation Store^[1]
• System V Release 4 (SVR4) .pkg files are cpio archives that contain specific file tree structures.^[2] They are software packages that can be installed, removed and tracked using the pkgadd, pkgrm, and pkginfo commands. The SVR4-based Solaris, and the Solaris-based illumos, support that package format.^[3]
• Symbian use .pkg files to store configuration information used to generate .sis installer packages.^[4]
• BeOS used .pkg files as part of their software packaging platform. The package format was used after Be Inc. bought Starcode Software Inc. and acquired their packaging tools.
• Apple Newton operating system used files ending in .pkg for Newton applications and software. As a result, when seen from the Mac OS X Finder, Newton applications appear the same as Mac OS X Installer packages; however, they do not share their file format.
• PTC/CoCreate 3D Modeling application use .pkg files to store model files. This .pkg file uses the ZIP file format.
• Microsoft is said to use .pkg files for profile storage on Xbox Network.
• L3 Avionics systems use some .pkg files for software updates.

• List of software package management systems