Social media platforms each have their own unique accessibility features and while we cannot fix if some key features are missing, we can do our best to make our content accessible before posting. Especially when social media is often used as a means of event outreach, posting accessible content ensures you reach the most people possible.
As social media apps are constantly updating, it is best to refer to guides from a social-media-focused group for the most accurate accessibility guidance. We recommend Accessible Social. Their education section has tutorials for all aspects of social media content and their guidebook and checklist are handy to reference as you create.
One principle that is universally applicable across all digital content and therefore all social media is proper use of color and contrast. On the smaller screens of social media viewing, color contrast issues will be amplified. Be sure to keep color in mind as you design and post.
Additionally, know that, if you are posting videos to social media, all of the previously described accessibility principles of videos still apply. However, audio description is not currently an option for any major social media platform. Follow the guidance on Accessible Social’s video descriptions page to figure out accessible work arounds.