For a "Raw" download, you want the full package (approx. 5GB) pre-verified and ready to mount.
Warning: Do not install the "Mac App Store Update" that offers Catalina or Big Sur. That will break your 32-bit app compatibility.
Here is how to get it safely and convert it into the format you need.
Stay safe, and keep that classic Mac running.
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume Third-Party Tools: Disk Drill can also be used to simplify this process. Key Specifications Using macOS High Sierra in 2025
