Anyone familiar with the WCAG 2.0 Guidelines know how important alt text on an image is for people who are blind or have low vision. Twitter has recently upped their accessibility and added an option that allows users to add descriptions to images allowing screen readers and braille displays to announce and display the text.
The feature is enabled by using the compose image descriptions option in the Twitter app’s accessibility settings. It is available in Twitter’s iOS and Android applications. Descriptions can be up to 420 characters.