Social media platforms have dominated the mobile ecosystem to the extent that it wouldn't be an exaggeration to say they are primarily services for mobile users. Therefore, the official guidelines of social media platforms recommend using video ratios optimized for mobile viewing.
Please check the official guidelines for each social media platform below:
Facebook & Instagram
For Feed: It is recommended to use a 4:5 ratio for videos.
For Stories and Reels: Since most users hold their phones vertically, using a 9:16 ratio to utilize the full screen is advisable.
For video slides format: A square 1:1 ratio is recommended, and it's best to use a consistent ratio for all videos in the slide.
For In-stream videos: A horizontal 16:9 ratio is recommended to ensure ads within the video are fully displayed.
For Meta Audience Network exposure: A vertical 9:16 ratio is recommended.
Instagram Shop: A square 1:1 ratio is recommended.
Youtube Shorts
Only videos up to 60 seconds are allowed.
A vertical 9:16 ratio is recommended, but a square 1:1 ratio is also acceptable.
Tiktok
You can upload videos up to 3 minutes, but short videos of 9-15 seconds are recommended.
A 9:16 ratio is recommended for videos, but 1:1 or 16:9 videos are also acceptable.