OnyX is a multifunction utility that you can use to verify the structure of the system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the Finder, Dock, Safari, and some of Apple's applications, to delete caches, to remove certain problematic folders and files, to rebuild various databases and indexes, and more. If you still need Sierra, follow these steps: Use this link to open the macOS Sierra page on the App Store: Get macOS Sierra. For security and compatibility reasons, Apple always recommends using the latest version of macOS. Now that High Sierra is available, you should upgrade to High Sierra instead of Sierra. And Sidecar, which lets you use iPad as a second Mac display.
Smart new features in the apps you use every day. Experience dedicated apps for music, TV, and podcasts. When you upgrade to macOS Catalina, you get more of everything you love about Mac.
