Remove useless files from a Mac
Onyx (free)

Verify the Startup Disk and the structure of its System files, to run misc. tasks of system maintenance

Configure some hidden parameters of the Finder, Dock, QuickTime, Safari, Mail, iTunes, Login window, Spotlight, and many of Apple’s applications

Delete caches, to remove a certain number of files and folders that may become cumbersome, and more.

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Removing duplicate files is not supported by Onyx.