You can have duplicate images on your computer for mostly three reasons:
#1. You transferred a set of pictures from the digital camera to your computer but did not erase them from the camera. Thus when you re-connected the camera, they got copied again to your hard drive but in a different location.
#2. You made some minor edits to a picture – let’s say you cropped it or fixed the rotation – and your image editing program saved the edited image as well as the original picture.
#3. You may also have images on your computer that are “loose duplicates” of each other. That means the images are mostly identical except for very minor variations – often happens when you capture multiple frames in quick succession.
1. Deleting Duplicate Images
If you are only looking to find and remove images that are “exact” duplicates of each other, Google’s Picasa desktop software could be a good solution. Just import all your picture folders into Picasa and then choose Tools –> Experimental –> Show Duplicate Files to see a list of potential duplicates.
While removing duplicate images with Picasa, please remember that the software will list all copies that are found of an image including the original one. You therefore need to keep one of these copies and delete the rest as demonstrated in the above screencast.
Alternatively, create a separate folder that’s not included in Picasa and move all the potential duplicate photographs to that folder instead of deleting them.
Related reading: How to Backup your Photos
Now Picasa is a good solution for deleting identical duplicates but your disk may also be storing have pictures that look similar visually but may differ as far as pixels or bytes are considered. Such files won’t be recognized by Picasa as duplicates but VisiPic, a tiny utility for Windows, can come really handy here.
2. Deleting Similar Images
To get started, launch the program and click File –> Add Folder to add folder(s) that you want to scan for duplicates. Then slide the Filter to somewhere between “Strict” and “Basic” so that program may group images that are similar or only slightly different. Hit play to begin scanning for duplicates.
To eliminate the duplicates, just move your mouse over the thumbnails and left-click the pictures you want to delete. They’ll be marked with a recycle bin icon and you may then either choose “Delete” or even “Move” to transfer them to a separate folder.
The tool is also smart enough to auto-select images for deletion that either have lower resolution or lower file-size than the original image.
Also see: Free-up Disk Space on your Computer