OnyX is a multifunction utility that you can use to verify the structure of the system files, run miscellaneous maintenance and cleaning tasks, configure parameters in the Finder, Dock, Safari, and some Apple applications, delete caches, to remove certain problematic folders and files, to rebuild various databases and indexes, and more.

OnyX is a reliable application that provides a clean interface to many tasks that would otherwise require complex commands to be typed using a command-line interface.

There is a specific version of OnyX for each major version of the operating system. Older versions not listed here can be downloaded from the Author link above.