For years, CCleaner was many people’s go-to program for cleaning up a Windows computer. It quickly finds and deletes temp files and other junk from a system. But these days, there are more reasons to get rid of it than keep it around.
First, it’s main function is replicated by a built-in Windows tool called Storage Sense. You can find this under Windows 10 by going to Start -> Settings -> System -> Storage. Turn it On, if it isn’t already. This allows Microsoft to clean your temp files for you, silently in the background, on a recurring basis.
But beyond being replaced, CCleaner may trigger your antivirus warnings. Microsoft and other companies sometimes mark CCleaner as a bad guy or a “Potentially Unwanted Program.” This may be because Microsoft takes a dim view of anything offering to “clean your registry” (please do not use this part of CCleaner!), or because CCleaner has a history of unsavory data collection.
I’ve also taken issue with CCleaner in past years, because it has led users to accidentally download Avast Antivirus onto their systems. This has caused conflicts for people with pre-existing antivirus on their systems, as two antivirus will usually fight each other and cause system problems.
TL;DR: CCleaner should be removed, and you can usually easily uninstall it by going to Start -> Settings -> Apps. You find it in the list of apps, click it, and then use the Uninstall button.