Universal binary

A Universal binary, as implemented by Apple during its transition to Intel processors that began in 2005, involved Mac OS X software that contained multiple sets of binary code that could run on more than one type of processor family.

History
The first Universal binary version of Mac OS X was Tiger 10.4.4. Rosetta was included to allow PowerPC software without Intel binaries to be run in emulation on Intel Macs. Universal binaries were phased out with the release of Mac OS X Lion which dropped out support for PowerPC software as well as Rosetta emulation.

With the introduction of full 64-bit Intel support in Mac OS X Snow Leopard, software could optionally include both 32-bit and 64-bit Intel binaries, though this was mostly transparent to the user. Users could opt to run such multiple-binary software in PowerPC or 32-bit Intel mode by checking appropriate boxes in the Get Info dialog box. The primary reason for doing so was for backwards compatibility with some plug-ins that were not updated with Universal binaries.

In 2020, Apple introduced Universal 2 with support for both 64-bit Intel and Apple processors.