The Snow Leopard ISO, also known as macOS 10.6, is a bootable image of the operating system that can be used to install or upgrade Macs. The ISO file contains the entire operating system, including the installation package, which can be used to create a bootable USB drive or DVD.
Since Apple no longer officially sells physical DVDs or digital downloads for 10.6, users must look to reliable archival sources:
There are several benefits to using Snow Leopard ISO: