Facebook uses a 9:16 aspect ratio for portrait-oriented content and 16:9 for landscape-oriented content, which should be uploaded with a minimum height of 450 pixels. This is necessary to achieve an optimal viewing experience without losing details. Incorrectly set or poorly optimized aspect ratios can significantly affect user engagement, making videos and images appear distorted or pixelated. Ensuring a correct aspect ratio can improve accessibility and benefit a wider audience, especially those watching on small screens.