The downloaded file is a disk image that contains an installation package. You must extract this package to place the actual installer app into your Applications folder.
Click and follow the on-screen instructions to upgrade your system. Method B: Clean Install Using a Bootable USB Shut down your Mac completely. Ensure your bootable USB drive is plugged in.
To get the full installer, you should use official Apple channels to ensure security and stability. Once installed, Sierra offers a refined experience that marked the official transition from "OS X" to "macOS". How to Download macOS 10.12 Sierra download macos 1012 sierra full
Run the gibMacOS.command file (Mac) or gibMacOS.bat (Windows).
If you're having trouble finding macOS Sierra in the Mac App Store, you can try downloading it directly from Apple's servers. However, please note that these links are subject to change, and it's always best to download from the Mac App Store. The downloaded file is a disk image that
Open your web browser and navigate to the official Apple Support page for older macOS versions. Locate the section.
Source: Apple CDN via GitHub Community Archives Method B: Clean Install Using a Bootable USB
Type Y to confirm that you want to erase the volume, then press .
Press , type your Mac's administrator password (no characters will display as you type), and press Enter again.