Why is the text size larger on some posts in my News Feed on Facebook?
When short text posts are shared on Facebook, the text size of these posts may appear larger in News Feed. You can't change the text size of these posts.
If you’d like to make all of your text on Facebook smaller or larger, learn how to zoom in and out.
If you're looking for ways to make using Facebook a more accessible experience, learn more about accessibility for people with disabilities.