With usage and time, Apple iOS devices iPhone, iPad and iPod touch accumulate long-term caches, temp and off-line junk files generated by Apps or due to failed iTunes syncs. Apart from taking up space on your device, they may devour memory resource and slow down the iPhone when launching Apps.
PhoneClean provides users with an fast, simple and free iOS device cleanup solution. The utility will clean App caches, cookies and off-line files; sweep off media temp files and reclaim other storage space on all your iOS devices.
To confirm wasted disk space on your device, Open iPhone (or iPad) Settings > General > Usage > And you’ll see as below:
Another way to check this wasted space is by using iTunes, open iTunes and connect your device via USB cable you will see the exact amount of wasted resources under "Other" heading.