Even if you can't find it in the "Purchased" tab of the App Store, Apple maintains a hidden support link.
Because Apple no longer provides Sierra publicly for new downloads, many turn to third-party websites (e.g., archive.org, certain Mac forums). Risk warning: Unofficial DMG files may contain malware, modified system files, or be corrupted. Always verify checksums if you go this route.
Once you have the DMG, here is how to install Sierra safely.
macOS Sierra (version 10.12) was released by Apple in September 2016. It introduced features like Siri on Mac, Auto Unlock with Apple Watch, Universal Clipboard, and iCloud Drive syncing of Desktop & Documents folders.
As of 2026, Sierra is considered obsolete by Apple. It receives no security updates, and many modern apps no longer support it. Only download if you need it for legacy hardware (e.g., older Macs that cannot run High Sierra or later) or specific legacy software.
Cause: Incomplete download. Solution: Re-download. Verify file size: Exactly 4,837,615,000 bytes for 10.12.6.
