The engineers at 1 Hacker Way trained their object recognition tech by feeding it millions of images as examples. This kind of machine learning is called neural network, and it was how Google taught AlphaGo the ancient game of Go and how one of our editors trained his computer to write Engadget articles. The team then made sure that alt text describes photos in a specific order, starting with (the number of) people, then objects and then scenes in the background.

People tend to post mostly images on Facebook these days to the point that browsing the News Feed has become a very visual experience. Someone who can't see all those could feel excluded, but this technology could help "the blind community experience Facebook the same way others enjoy it." While the tool is only available for iOS and only in English right now, the social network plans to release it on other platforms and in other languages in the future.