Storage Cleaner
Storage Cleaner is a tool that allows you to clean up any junk (useless) files located in the storage. It searches whole storage and categorize junk files into different categories.
READ_EXTERNAL_STORAGE WRITE_EXTERNAL_STORAGE
Junk files are files that have no use anymore but still stay in the storage. Junk files can be generated by user mistakenly or misbehaving apps. Some apps tried to create temporarily files, but it did not handle the file properly (i.e. delete the file) after finish. Hence, these files are now useless and will accumulate into significant size over time. Most common example are log file, cache file, and temporarily file. Almost in every cases, these files can be safely deleted.