Duplicate Files in Google Photos
Google Photos can smartly detect duplicate photos and will skip uploading them if a copy has been uploaded previously. The file names of your photos can be different and they can reside in different folders of your hard disk but the service will still recognize the duplicates and remove them from the upload queue.
There are two kinds of duplicates – exact duplicates and near duplicates. If you take a file and slightly crop it or change the EXIF data, it is a near duplicate of the original file. Google Photos will however treat this is a different photo and upload it as well along with the original image.