CAUTION: has been infected by a malware:
https://arstechnica.com/information-technology/2017/09/backdoor-malware-planted-in-legitimate-software-updates-to-ccleaner/

This program is a useless placebo for non-technical users...

Don't get me wrong, the software itself is kind of okay. But I find it highly ironical that the installer installs Big Brother Google Chrome (and sets it as default browser) by default... Plus it must leave tracks somewhere, because when you uninstall CCleaner and then try to reinstall it again, it doesn't ask again to install Chrome... Pretty dirty for a "cleaning" software...

users of windows 8 or newer, should never clear the registry!
If you try to clean registry, then your boot will slow down.

I've had my issues with CCleaner. Generally speaking it does its job but it's not the all-in-one disk cleaning solution some tout it to be. I've often found that it is very 'surface level' in that it cleans many different parts of your computer but many underline portions are still left intact. Still, if you want a quick and easy solution for these things then it's a good option; just be aware it's not going to clean everything.

Comparison ........................................................ Pt. CCleaner ....... Pt. Glary Utilities
Disk Space .............................................................. 1 2.87 MB ............ 0 15.7 MB
Autostart Delay Function.......................................... 0 No .................... 1 Yes, is useful
Automatical cleaning, when the Computer starts .... 0 Selectable ........ 1 No, is safer
Cookies Delete Selectable for each browser .......... 0 No ..................... 1 Selectable, is safer
Analyze functions, what cookies to delete ............. 0 No, not so safe . 1 Selectable, what category
Detection of obsolete McAffee software in registry 1 Yes = OK .......... 0 No, not OK
Declared used as unused file extensions ................ 0 30 = Error ......... 1 5, really unused, OK
Could find numerous entries of uninstalled Nero.......1 with Active-X..... 0 Not detected
Assessment Points for all features ................ 3 Not my favorite . 5 My favorite
I had a bad experience after deleting entries, that CCleaner suggested to delete:
System was not bootable any more, so I had to restore Drive C from a Macrium Refl. backup.
With Glary Utilities until now I could follow all proposals without getting a problem. Otherwise, Glary Utilities was not able to find many left entries after uninstalling Nero, but CCleaner was here successful.
Be careful to follow CCleaner suggestions !</b

Since the last issue http://www.spamfighter.com/News-21150-CCleaner-Compromised-Hackers-Collect-Data-from-Affected-PCs.htm that wasn't the first one. Unfortunately, I do not trust Piriform's software anymore. I've had a lot of problems due to downloading the .exe compromised .exe file.

I don't know about the newest version, but it destroyed my registry few times in the past, the way my system couldn't start. I replaced it with RegCleaner and later with PowerTools Lite 2013, which were free but are both outdated by now.

I'm having trouble with my computer right now.. I'm a college student and I go to the same 3-5 sites just about evey time I'm on the internet. I frequently have to save files for class, notes, research etc. My computer is running slow and according to AVG Anti-virus, I'm "not fully protected". I've been trying for the past hour to "fix" the problem through AVG and it's just not working. I'm not sure why. With all of that being said, Im wondering if I use CCleaner to clean out my computer if it'll delete or "clean" out documents, website memory, &/or files that I've downloaded that I need. Can anyone help?

This is a great piece of software. Does an amazing job at getting rid of unnecessary files and superb for a computer tune-up.

@Aaron, I use this on a daily basis on several computers a day and never have had it mess up a computer. Perhaps there were other underlying issues with their computers?

I dont like this program because it usually removes things that should not be deleted and I have known a good many friends that it has screwed up their system, and they have to reformat their system, and start over. I dont recommend it, there are better cleaners out there.

Since Avast acquired the company its not the same. It has bloat to it, and also my Antivirus program picked up malware in the installer file; which might be a false positive. So I'm looking for an alternative now, sucks was a really good app at one time.

[Edited by Krimsun, March 27]

I was using Ccleaner since several years ago, but now I stop ! Their policy are set against their users..
The last version (5.4.1) include adware (Google chrome)

I have used CCleaner for years and it's always the first program that I recommend to others to help clean the junk files off of their PC's and clean their browser cache etc. It is simple, yet effective and is constantly updated.