Why do I need to clean my computer?

Everyday use of your web browser and system builds up junk files:

If you've also installed lots of applications that you've forgotten about or no longer use, these applications also keep files that you don't need.

CCleaner removes these junk files and also helps protect your privacy: 

It cleans your browsing history and temporary internet files, allowing you to delete traces of the login details from your online accounts and other data. This helps you feel more confident online and less susceptible to identity theft.