Video and Image Specifications for Ad Placements | Facebook Help Center
— Read on m.facebook.com/business/help/103816146375741
Video preparation
https://en-gb.facebook.com/business/learn/facebook-tips-videos-preparation
Create video advert
https://en-gb.facebook.com/business/m/how-to-create-videos
Video requirements
https://www.facebook.com/business/help/430958953753149
Tips for better mobile video
https://www.facebook.com/business/help/144240239372256