When it comes to system junk files cleaning software on Windows, many users will recommend Piriform's CCleaner first - which has almost become one of must-have tools for any computer. CCleaner is free, small, has multi-language interface, and runs fast. Especially, it is fairly stable and safe to use, even the novice computer user won't encounter a problem due to misuse. CCleaner for Mac is a free system useless files cleaner, system optimizer and privacy protector specially designed and developed for Mac users. It is actually the Mac version of CCleaner.