There is a CCleaner for Android and the app does a great job for cleaning your smartphone or tablet of useless files.
You can download the app from here, Google Play, free.
It should display “Cache”, “Browser History”, “Downloaded Files”, “Apk files”, “Empty folders”, “Processes” and after the line, Chrome and YouTube.
What you need to select is “Cache”, “Empty folders”, anything where is saying “thumbnails” and other cache options.
You usually don’t want to lose your browser’s history, the downloaded files and the apk files.
After running the app, my tablet got rid of around 2 gigabytes of useless files. Different caches where just occupying a lot of space.
CCleaner for Android is a great app if you want to optimize. Be sure to uninstall any useless apps before running CCleaner.