Common aspect ratios and when to use them
9:16 fits Shorts, Reels, TikTok, and other full-screen vertical feeds. 1:1 is stable for square feed posts and thumbnail-style clips. 4:5 uses more vertical space in Instagram feeds. 16:9 remains the standard for YouTube, presentations, and website embeds.
If one source video will be published in several places, keep the master file and export a separate crop for each ratio. Safe areas differ by app, so a caption that works in one crop can be covered by buttons or descriptions in another.