Adding alt text on Mastodon has been around roughly as long as Twitter. It took about 10 months to roll out between 2016 and 2017. What I love about the issue discussion is that once the matter was raised, nobody argued against it.
One of the joys of open source software is that the user gets to participate in and have a window into the development process.
Anyway, taking inspiration from those discussions I've injected some CSS (https://gist.github.com/FiXato/3de505b04efefd49a1e3568b70545234) to a11y.social that surrounds images with a dotted red border if they DO NOT have alt text.
As a sighted user, I found Twitter's ALT button useful for deciding whether or not to offer up a description in a reply.
Here is a quick test. If you are browsing Mastodon from the a11y.social instance you should see a red border around the image attached to this post. If you are on a different instance, tell your admin to add the CSS linked in my previous toot!
Alt text (intentionally excluded from image): a German Shepherd asleep on a couch with a tennis ball in its mouth.
One more test, same picture.
Interesting. So because I edited the first post, an empty alt attribute was added to the image which breaks the highlighting rule in CSS.
@mark Thanks for adding the Alt text feature. Really helpful.
A Mastodon community for all with a focus on accessibility, assistive technology, and the interests of the broader disability community.