CCleaner is a free system optimization tool for Windows, Mac, and Android. It helps users clean up their system by removing junk files and temporary files, freeing up disk space and improving system performance. CCleaner also has additional features such as a registry cleaner, startup manager, program uninstaller, disk analysis, and disk wiping. It can even be used to protect your privacy by deleting browsing history, cookies, and other private data. CCleaner is a powerful and easy-to-use tool that is trusted by millions of users around the world.