The function, called Automatic Alternative Text, works via VoiceOver and generates descriptions of photos that are spoken out loud as a user swipes past photos in the Facebook app.
Previously, people using VoiceOver would only hear the name of the person who shared the photo, followed by the term "photo", when they came upon an image in the News Feed.
Thanks to the new function – made possible by advancements in object recognition technology – a richer description is now available. For example, a user may hear, "Image may contain three people, smiling, outdoors."
Automatic alternative text is currently only available in English, but Facebook plans to add the function for other languages soon. To use the feature on an iOS device with the Facebook app installed, go to Settings -> General -> Accessibility -> VoiceOver and turn on the VoiceOver function.
Facebook is free on the App Store for iPhone and iPad. [Direct Link]