CCleaner's primary function is to remove unwanted and unused files that are slowing down a computer. Premium versions of CCleaner also offer other features, such as automatic updates, disk defragmentation and file recovery.
CCleaner first looks for files that haven't been used in a long period of time while taking up valuable hard drive space. The program erases these files, which allows the computer to function more smoothly. CCleaner also erases the search history and cookies on the computer's Internet browsers. However, CCleaner 3.0 has the option to scan for cookies that are advantageous to the user and skip their removal, including cookies from Google or other search engines.
CCleaner also locates registry errors and either fixes or removes the errors so that the computer can run in a more stable fashion. Errors detected by CCleaner include missing references to shared DLL files or missing application paths. CCleaner also has the option to disable unnecessary programs that run during a computer's startup.
CCleaner's interface lets the user select files that are off-limits to the cleaning software, such as recent documents, saved passwords or cookies for certain websites. CCleaner can scan an area prior to cleaning so that pertinent files are not erased. CCleaner is also capable of erasing an entire drive if the user requests it.