Note: This works on macOS High Sierra or newer. If the command fails, use the manual URL method.

If you try to run the installer from a USB drive and get the "damaged" error:

While macOS 10.12 Sierra is an older operating system (released in 2016), it is still frequently sought after for legacy hardware support or specific software compatibility.

Apple still hosts Sierra on its servers. Use this link in (it may redirect to the App Store):

✅ This is a (still active as of 2025). Download the .dmg , open it, and run the InstallOS.pkg to place the installer in /Applications .

http://updates-http.cdn-apple.com/2019/cert/061-39476-20191023-48f365f4-0015-4c41-9f44-39e3e7a6d0b9/InstallOS.dmg