CCleaner

Since Avast purchased Piriform CCleaner in July 2017, updates and installs cannot be trusted anymore.
Reports of CCleaner updates installing Avast AV ... with default opt-in

CCleaner/Avast are phoning home with user data
At first only PRO could be opted out, but more recently free CC now has opt-out.
Avast have been ducking and weaving with CCleaner since they took over Piriform 10 months ago
Portable CC has also been discontinued :(

What will they get up to next ?
Very disappointing with this very long term favorite being treated as a cash cow by Avast

CC installer used to offer Google Toolbar *opt-in" but Avast have changed that to opt-out or you get their AV and consequences of 2 AVs on your machine.
I can no longer trust Avast/Piriform ...

The end of a dynasty :(

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.

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

STAY AWAY FROM IT!!!!
I opened this accound just tu give this review to tell you how much I hate these guys!
It installed AVAST without even asking me!!! [YES I checked to the "more options" while installing it, I checked everywhere and never saw AVAST listed]
This company is a total failure, I will uninstall all of their programs from my PC.
Avast, Ccleaner, Speccy, Defraggler, Recuva,..,., all of them! They even spread a virus to millions of users last year. Stay away from them.

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...

CCleaner use to be a great application for cleaning your computer, with my favorite feature being their secure uninstaller which checked the registry etc to completely uninstall an application rather than only deleting the main contents.
However over the years it has gotten more and more intrusive. It's now basically spyware, always running in the background even when you tell it not to. There was also an incident where they were serving the application with a virus and backdoor by accident for several months.
It was one of the best applications of it's kind for it's clean UI etc but too much features are locked off to other editions, it's insecure, and it's always sending your data home. There are many great alternatives, but most delete too many files including app data and system files by accident. In general it's not necessary to have a system cleaner, Windows and other applications already do automatic garbage collection. You're best off manually cleaning your browser history etc. CCleaner is a last resort to install on your grandpas computer if it's on it's last legs.
Two open source/ safe alternatives to CCleaner's features are BleachBit[file deletion] and BCUninstaller[uninstalling with left over checks]. At this time there's no open source registry cleaner; though registry cleaners tend to break stuff often, use BCUninstaller to mitigate leftover registry entries from uninstalling software.

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)

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

Used to be the best.
Now there are better choices.

It doesn’t work as it should and it too intrusive.

It was better when I downloaded. Now there are a lot of advertising!

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

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 file.

[Edited by mlemmark, May 31]

I used to use it all the time then stopped because it started screwing up my settings.

I've recently downloaded it again and now I'm uninstalling it.

My PC runs like a snail with CCleaner installed, the program is running all the time and I can't stop it because "access is denied".

It messed up all my windows settings, again!

Another example of good software gone bad.