So I downloaded a iso from apple.com the title is:How to get old versions of macOS so I downloaded it I click the sierra download then my mac running high sierra so how to create a bootable usb to downgrade cause this computer is kinda slow on a clean install of high sierra.
To perform this action will require booting from a Bootable Installer.
This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer. Example : Bootable Installer of Sierra would have to be done on a computer that Qualifies to run Sierra.
Once that is done read on for preparing the Destination computer
>> Only works on Intel Based Apple Computers.
1 - Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.
2- Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive.
3 - It will present options >> Disk Utilities >> View >> View ALL attached Drives.
4 - Choose the Upper Most Drive ( not the volumes indented and list below ).
5 - Formatting for macOS 10.13 High Sierra and below requires HFS Journaled with the GUID Partition Map
6 - Once that is done >> backup out of Disk Utilities and choose install macOS.
7 - Follow the prompts and it may automatically reboot several time.
8 - Upon a final reboot - Setup Assist will present with the newer version of macOS.
How to create a bootable sierra usb
