installing macOS Sierra on an external disk

[Rturner003]

i want to install macOS Sierra from an external disk. When I downloaded the os from Apple it tells me that the os is to old, I have High Sierra installed on my macBook Pro. How can I get a version of Sierra to install on my external disk to be able to boot up when I require.

 

[Just_Me_D]

i want to install macOS Sierra from an external disk. When I downloaded the os from Apple it tells me that the os is to old, I have High Sierra installed on my macBook Pro. How can I get a version of Sierra to install on my external disk to be able to boot up when I require.

When you attempt to install MacOS Sierra, are you attempting to install it over High Sierra? In addition, after it tells you that’s its too old, does it prevents you from installing it or does it simply alert you that you’re attempting to install an older OS version?