I saw a lot of toots recently talking about the alt text feature on Mastodon with some good information about how you add a description, but I also noticed there's a great amount of people with some doubts about the best way to describe media.
I decided to make a post on my blog gathering some information about it on both Twitter and Mastodon and answering some questions people frequently asked: https://anna.flourishing.stream/2017/11/03/accessible-media/ I hope it helps! #accessibility #disability