When you scroll through your photo gallery, you don't want to wait for the phone to decode a 48MP RAW image every time. Instead, Android generates small previews—thumbnails. It stores these previews in a proprietary database format. This is the thumbdata file.
For advanced users, binwalk (a free firmware analysis tool) can carve JPEG images out of raw thumbdata files. thumbdata viewer free
Are you trying to , or are you looking to clear up storage space on your phone? Thumbdata3 Viewer - Online JPEG extractor When you scroll through your photo gallery, you
A: Generally, no. They contain a visual history of images that were on your phone. Even if you deleted the original image, the thumbnail remains. If you are selling a phone or transferring files, it is best to delete the .thumbnails folder entirely. This is the thumbdata file