If you need to perform a "clean install" or fix a Mac that won't boot, you can create a bootable USB drive (at least 8GB or 16GB required).
Other websites, like CleanMyMac or AppleSeed, might offer the macOS Sierra 10.12 DMG file for download. However, exercise caution when using these sources: mac os sierra 1012dmg download free
Before downloading, ensure your Mac supports Sierra 10.12. Generally, the following models are compatible: : Late 2009 or newer. MacBook Air / Pro / mini / Mac Pro : 2010 or newer. Important Technical Notes If you need to perform a "clean install"
macOS Sierra (10.12) is available for free through official Apple channels, often provided as a InstallOS.dmg file that contains the installer package. Released in 2016, this version introduced major features focused on Siri integration and cross-device continuity. Generally, the following models are compatible: : Late