From the developers of Best Battery Saver App: Battery Doctor comes another useful app called Clean Master which is probably the best system cleaner app for android free at the Google Play store. If you have a lot of junk in your system (android), then clean master will find it and clean it. Junk files that this app detects include system and app caches, residual files, your privacy data such as browser history and app’s account passwords and messages.
If you are one of those people who like to try out different ROMs and regularly install or reinstall different versions of android, you might have loads of residual files remaining from previous installs. Without Clean Master searching for each folder or unwanted files will take a lot of time. Overtime system cache tends to build up to GBs of unwanted data and you need to regularly clean your cache to save storage. Clean Master will remind you from time to time to clean your cache.
Clean master comes with a widget which allows you to kill background tasks will one touch and free up loads of memory so that your system runs smoothly.This is a very useful app and I recommend everyone to install it right away.
UPDATE: The latest Clean Master updates include- Improved scanning speed, apps to SD card feature and cleaning the video cache of Instagram.