Facebook Mobile ads and Page posts will appear differently from 19th August 2019 with major changes to text and media ratio.
Text
With the new change, only 3 lines of primary text will appear on Facebook mobile NewsFeed. Additional text can be viewed by clicking on the Read More option.
The caption of the ad is similar to the description seen below a link on Google Search, it defines the clickability of the post. And, fewer lines of text means quicker information that people might not skip.
The fewer lines of text would also make the feed look less cluttered. While marketers who want to add more text can still do so.
Also Read: Facebook introduces additional monetization avenues for creators
Media
The maximum media height for photos and videos is being reduced to 4:5 on mobile NewsFeed. As the tallest supported aspect ratio for images without links and for videos is now vertical (4:5), media taller than that will be masked on Facebook mobile News Feed.
This change wouldn't really affect or benefit advertisers or marketers as such. As you would just have to create media in a different size than before. Although, it would make the feed of the user look more uniform.
Currently, there are various sizes in which a marketer can create media in ads. For instance, 1:1, 4:5 and more. This provides flexibility to the marketer to use a suitable ratio for each post while not compromising on it's look but it made the feed look varied.
The change would appeal to the feed's aesthetics. Facebook claims, "This will help drive increased ad effectiveness and make it easier to use the same assets on Facebook News Feed and Instagram feed."