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by acruns 2087 days ago
They don't for standard picture but they do embbed their own metadata

https://iptc.org/news/what-does-facebook-do-with-your-photo-...

https://www.carlseibert.com/facebooks-hidden-metadata-codes/

You may be thinking of PhotoDNA which is used for different purposes

https://www.microsoft.com/en-us/photodna