“I started on the Purchased tab in the Mac App Store app, where you can (theoretically) see all past purchases, including prior Mac OS X versions,” Griffiths writes. “However, those old releases stop with Mac OS X El Capitan from 2015; neither Sierra nor High Sierra are listed.”
“Next I tried searching the Mac App Store for Sierra, but that nets only Server and High Sierra, and a few apps that appear to have gotten away with using ‘Sierra’ in their descriptions,” Griffiths writes. “Given how much trouble I had finding this page, I thought I’d post it here for anyone looking for Sierra.”
How to download macOS Sierra here.
MacDailyNews Note: Apple recommends High Sierra, the latest version of macOS, to get the latest security and compatibility enhancements.