Registry cleaning rules

This page briefly explains what the Registry Cleaner is, what 'cleaning rules' are, and clearly explains the specific options it gives you. If you only want to view the cleaning rules, skip to Files and data that you can clean in the Windows Registry below.

What is the Registry Cleaner?

The Windows Registry contains files that act as settings for your computer's operating system, such as when you choose to run an antivirus program or what you've chosen as your desktop background. Installing, upgrading, or uninstalling software on your computer can cause files stored in the Registry to get broken or go missing, which causes errors. The Registry Cleaner is designed to clean this part of your operating system to help prevent errors. 

What are 'cleaning rules'?

These are the specific files and data that you allow CCleaner to clean from your system (or fix), as is the case with the Registry Cleaner. You can see some in the screenshot below as selectable options in Registry > Registry Cleaner.

CCleaner Professional, Registry, Registry Cleaner window. See information below.

Files and data that you can clean in the Windows Registry:

Click the Registry icon to see all the available Registry cleaning rules that CCleaner for Windows can use.

  • Missing Shared DLLs - Removes entries for libraries, which are shared by multiple programs but no longer exist
  • Unused File Extensions - Removes entries for file extensions that are no longer associated with applications
  • ActiveX and Class Issues - Removes invalid entries for COM/ActiveX object that refer to non-existing files
  • Type Libraries - Removes invalid entries for type libraries that refer to non-existing files
  • Applications - Removes invalid entries for non-existent programs
  • Fonts - Removes invalid entries for fonts that no longer exist in the Windows Fonts folder
  • Application Paths - Removes entries for registered application paths that no longer exist
  • Help Files - Removes entries referring to help files that no longer exist
  • Installer - Removes unnecessary uninstallers or the remnants of leftover uninstallations
  • Obsolete Software - Removes entries for applications that are no longer installed
  • Run At Startup - Removes entries for system startup applications that no longer exist
  • Start Menu Ordering - Removes entries for Start menu applications that no longer exist
  • MUI Cache - Removes invalid entries from a cache of recently run programs
  • Sound Events - Removes references to sound files that do not exist
  • Windows Services - Removes Windows Services, for which the executables are no longer present
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