A free app for Android, by Smin photo recovery.

Full storage? Perhaps your phone is filled with duplicate content. If you want to get rid of these files fast, you’ll need Duplicate File Remover. This app lets you scan and delete all duplicate images, videos, and more on your device, freeing up precious SD or internal storage. 

You can select which file you want to keep, all thanks to the little checkbox beside the file name and location. If you want, you can share a particular file with a loved one. The app’s user interface makes it easy for most people to preview and delete unwanted documents, pictures, and videos. This application is currently free to download and use on the Play Store.