Since OnyX accesses numerous functions and options of the operating system, the appropriate administrator rights are required.
The first version measures only 1,2 MB while for example version 3.1.9 for Mac OS X 10.11 El Capitan is 33,1 MB. The size of the download also varies depending on the operating system from macOS X 10.2 (OnyX 1.3.1) to macOS 10.13 High Sierra (OnyX 3.4.4). You can find the download of the app at /en/onyx.html - Everything is described there in English and you can only switch to French, but once you have downloaded OnyX, it can automatically also be used in German. Even if it gets slower due to age, you can deactivate various effects and other unnecessary settings with OnyX in order to free up system performance. Whether settings and optimizations with regard to the file system, settings for effects, appearance and other behavior of individual applications or access to system aids such as memory management, network utility and color picker - there are many practical steps possible to use the Mac and your workflow on the machine can optimize.
The free OnyX app from Titanium Software offers useful setup options on the Apple Mac without registration and without harmful or annoying additional software. Sir Apfelot recommendation: Clean up your Mac hard drive with CleanMyMac OnyX for Mac OS X and macOS