Facebook assigns a numerical ID to all photos uploaded to the social media channel. Images downloaded from Facebook have that numerical ID as part of the file name by default. If you know this number, you can use it to find the source of the picture on Facebook. It might be the profile picture of the person who shared it or the person whose profile you are trying to find might be named or tagged in the image.

Reverse Image Search: Facebook and Google Method

You can perform a reverse image search in Google using a photo posted on Facebook to possibly learn more about who posted it.

If neither approach lets you find someone by picture, there are other tools you can use to perform a reverse image search, Facebook or otherwise. For instance, you can upload an image to TinEye and find out where it has appeared online.