1st. CCleaner is one of the most popular PC & registry cleaner softwares of all.
2nd. Windows doesn't offer a built-in registry cleaning software.
3rd. CCleaner is made so that it shouldn't (and will not) harm your computer. And, it's also virus free.
4th. If the program is popular and has gained good reviews, you can trust it.
Cleaning the registry does not in any way speed up or improve windows, and it never will. It can however hurt your computer. Though they obviously try to avoid breaking your PC, "registry cleaners" are snake oil. Potentially dangerous snake oil. The registry does not need to be cleaned, therefore trying to clean it can only result in a) nothing or b) damage. Obviously windows doesn't include it, because the very idea is stupid.
Similarly, the file cleaner part of ccleaner also tries to not break your computer, so you'll keep using it. But why would you use it when you have the built in 'disk cleaner'? Using that you don't have to install any extra software, or worry that a ccleaner update might have an unfortunate mistake. Using disk cleaner is also more efficient and less conflicting because it knows which files are currently in use by the system (or scheduled to be) and which aren't. All ccleaner can do is not delete files less than two days old- which, depending on your system could be BOTH still in use (if you run ccleaner religiously you may be preventing windows from ever completing certain tasks) or leaving large files on your system that aren't needed any more, simply because they aren't two days old yet.
Alternatively, don't manually run disk cleaner- let windows automatically handle it. Because it will, eventually. Most people have an excess of space, and would actually gain a speed benefit from NOT clearing their caches- but they have the *** backwards idea that their HDD/SSD needs to be "clean" for some inane reason.
Every third party program ccleaner can clean has self regulating and manual cache management. It is infinitely more wise to use each program's built in cleaning mechanism- ccleaner may have a good track record, but there is still potential for some conflict (be it minor or major).
Just because a program is popular doesn't make it good. Many things are built upon a foundation of lies or misconceptions, and people just eat it up and write good reviews. Not everyone is well informed on the subject (frequently, even the authors of the software are unaware that they fundamentally misunderstand what they are trying to "fix"), so they don't know any better and just believe whatever the website tells them. I'm sure there are many good reviews for various RAM cleaning software, for example, but clean your RAM all you want; it isn't going to make your PC faster.
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