You might find yourself with an accidental set (or many sets) of almost-duplicate files and folders. It’s a common side-effect of changing to new devices, new back-up media, or new backup methods. It can happen when rescuing old hard drives, or recovering from a crash. It can happen with cloud storage hijinks, or with photos being simultaneously on phone & computer. And sometimes it’s from accidentally clickety-click downloading that recipe 17 times.
In order to go forward with a tidy set of files which contain those files you need, and not multiples upon multiples, we de-duplicate. This can be done by hand (one at a time, open the file, eyeball it, decide if it matches the suspected duplicate), but that way lies madness. MADNESS.
I can comb through your files and remove only those duplicates which have contents which are byte-for-byte exact copies of each other. While doing so, I can make the fine distinctions between apparent duplicates that need to be kept (within application folders, for instance), and true redundancies.
This can also be done in a completely non-destructive way. where all your media are copied to a fresh drive, cleaned and deduplicated, and then both the old and the new disks and drives are given back to you.