While the OS itself is free from Apple, third-party sites advertising "Free Downloads" pose significant security risks: Download macOS Sierra 10.12.5 Update for 2017 iMacs
Standalone installers are available, such as the macOS Sierra 10.12.5 Combo Update , which allows updating from any prior version of Sierra. advertisement macOS Sierra 10.12.5 Free Download
Apple provides the software for free to users with compatible hardware. You can obtain it safely through: While the OS itself is free from Apple,
The most direct method; check the "Updates" tab for the built-in Software Update function. advertisement macOS Sierra 10.12.5 Free Download