Videos are one of the most important content on fb mostly only Youtube Vimeo or other videoportals are whitelistet to distribute video on the platform. Many Iphone user post also ther videos directly . Much more aspect ratios are possible and gain more interesst than the standard 4:3 or 16:9 size . Iphone is vertical and a special interest as a special new wide spread Format. Here a listing for conformed Formats. At the moment max size on wide or high is 398 pixel. What is the minimum size we will test soon.
398 x 298 px Standard Youtube Format 4:3
224 x 398 px Iphone Format
398 x 398 px Squere Format