From August 19, 2019, Facebook is changing the aspect ratios on the mobile news feed.
The text will change from seven lines to only three, and and the picture/video aspect ratio will change from 2:3 to 4:5.
In effect, this means fewer text lines visible and to see any more, a user will have select "See More."
Facebook says it'll simplify formats, however, I suspect that the reduction in side is to allow more ads in the feed.
[
facebook.com...]
