Professional CCleaner

[Melanie Deer]

I paid for CCleaner Professional to automatically clean my computer but I would like to ask what it actually does because when I also do it manually there is always a lot left to clean even though it's just been done 'automatically' so what actually am I paying for?   

[nukecad]

It all depends on how you have set up Smart Cleaning, and which option you are using for manual cleans.

Smart Cleaning will monitor your computer and can automatically remove junk when it reaches a certain level of GigaBytes.
With CCleaner Pro you can set what that level is, you can also set if it cleans automatically or prompts you to clean.

If the junk has not reached that level, or if it's been automatically cleaned and is building up to the level again, then it won't be cleaned automatically and so there will always be something to be found by a manual clean.

Smart Cleaning cannot clean browser files while the browser is still open, so there is also a section to say what it should do when you close a browser.
If you haven't set automatic browser cleaning on closing then after you have closed the browser a manual clean will find those browser files and cookies to clean.
 

Finally it may also depend on what method you are using for a manual clean.

Smart Cleaning uses the options, ticks/unticks, that you have set in Custom Clean.

If you use Health Check for manual cleaning then it uses it's own rules so may(will) find different things.

[IreneAdler]

Maybe it's not set up properly? I had the same issue with it, but a friend of mine that knows more than me in this helped me to figure it out. I also had to do a lot of cleaning manually, but after he set it up properly, I don't have to do that anymore. I'm not an expert but when I was looking for a registry cleaner free, the ccleaner was rated as the most popular registry cleaners among users globally, so I got it. It works great for me, so try to set it up properly and you'll see results from the first time.

[nukecad]

Registry cleaning is not needed for a working computer, it will not save more than a few KB of space, and will not speed up a computer in any way.

Registry cleaning is a tool for use when fixing a broken computer, using it indiscriminately on a working computer can stop that computer working.

It is especially recommended that you do not use any registry cleaner with Windows 10, see this from Microsoft:
https://support.microsoft.com/en-gb/help/2563254/microsoft-support-policy-for-the-use-of-registry-cleaning-utilities