Downloading the full installer for macOS 10.12 Sierra (roughly 5 GB) is necessary for creating bootable USB drives or upgrading older Macs. As of 2026, Apple maintains this legacy software for supported systems. 1. Official Download Source (Recommended)
Use this Apple Support article to download the InstallMacOS.dmg file. download macos 1012 sierra full
Once this process is complete, you have a "full" version of macOS Sierra that can be used to boot a Mac and perform a clean installation. Downloading the full installer for macOS 10
Note: If this returns an error, Apple may have finally deprecated the certificate for 10.12. In that case, proceed to Method 2. proceed to Method 2.