AI Video Aspect Ratios: What to Generate for Each Platform in 2026

This is the least glamorous decision in the whole pipeline and one of the few that is genuinely hard to undo. Generate a clip in the wrong ratio and every fix from that point on is lossy: you crop, you letterbox, or you regenerate and pay twice.

The rule is one line long — generate in the ratio you will publish in — and most of this article is about the cases where people talk themselves out of it.

The short version

If you only ever ship to short-form: generate everything 9:16 and stop reading. That single choice covers TikTok, Reels, Shorts and Facebook Reels, which is where nearly all the volume is anyway.

Why cropping afterwards is worse than it looks

Cropping a 16:9 generation to 9:16 throws away about 70% of the frame width. That is not a framing adjustment — it's a different shot.

Worse, the model composed for the frame you asked for. A generated wide shot puts the subject where a wide shot wants it, with the interesting material spread horizontally. Crop it to a vertical strip and you keep the subject's torso and lose the two things that made the shot work.

And you lose resolution exactly where it hurts. A 1080p 16:9 frame cropped to vertical leaves you roughly 608 pixels wide, upscaled back to 1080 for delivery. That is a soft image on a phone screen, and it is the single most common reason a generated clip looks "off" without anyone being able to say why.

The one case for generating wide and cropping

There is exactly one: when you need the same clip in both 16:9 and 9:16 and the subject is centred and static — a product on a surface, a slow push on a single object.

Even then, generate the 9:16 as the primary and treat the 16:9 as the derivative, not the other way round. Vertical is where the frame is tightest, so compose for the tight one and let the loose one inherit. If you need a genuine reframe rather than a crop, that's a job for a dedicated reframing pass, not a manual crop in an editor.

Safe areas: the numbers I actually use

The frame is 1080x1920, but the readable frame is a lot smaller than that, because both TikTok and Instagram put their own interface over the bottom of your video.

Keep everything that must be read between roughly 12% and 78% of the frame height. On a 1080x1920 canvas that means staying clear of the bottom ~420 pixels. TikTok's button column also eats about 180 pixels on the right, so centre your text rather than right-aligning it.

This applies to end cards more than anything else, because an end card is pure text and it is the last thing anyone sees. A call to action sitting at the bottom of the frame is a call to action nobody read.

Captions are the exception that proves the rule: a lower-third caption band sits just above that dead zone, around 60-70% of the height. Push it lower and the platform UI starts covering words.

Resolution, and why 720p is usually enough

For short-form, 720p at 9:16 is fine and often indistinguishable from 1080p after the platform re-encodes it. Every platform transcodes aggressively; you are not delivering your file to the viewer, you are delivering it to an encoder.

Where resolution does matter: anything with fine text burned in, anything you'll crop later, and anything destined for a paid placement where it may be shown larger. For those, generate at the higher tier. For daily organic volume, 720p 9:16 is the sensible default and it costs less per clip — which matters when you're shipping several a day. See how many AI videos per day.

Ask the model for the ratio, then check the pixels

Do not trust the request. Set the aspect ratio explicitly in the generation settings rather than describing it in the prompt — "vertical video" in a prompt is a suggestion, the aspect ratio field is an instruction — and then verify the output.

One command, and it has caught more mistakes for me than any amount of eyeballing:

ffprobe -v error -show_entries stream=width,height -of csv=p=0 clip.mp4

Height must be greater than width for anything vertical. I check this on every clip before it goes anywhere near a scheduler, because a landscape clip discovered after publishing is a deleted post, not an edit. More on getting the request right in AI video prompt guide.

FAQ

What aspect ratio should AI videos be?
9:16 for TikTok, Instagram Reels, YouTube Shorts and Facebook Reels — which covers almost all short-form volume. 16:9 only for long-form YouTube, and 4:5 or 1:1 for static feed posts.

Can I crop a 16:9 AI video to 9:16?
You can, but you throw away about 70% of the width and drop to roughly 608 pixels of real horizontal resolution. Generate vertical in the first place unless the subject is centred and static.

What resolution should I generate at?
720p is enough for organic short-form, because platforms re-encode everything anyway. Go higher for burned-in fine text, for anything you'll crop, and for paid placements.

Where do TikTok and Instagram cover the video?
The bottom roughly 420 pixels of a 1080x1920 frame, plus about 180 pixels on the right for TikTok's button column. Keep readable content between 12% and 78% of the frame height and centred.

Is 4:5 better than 1:1 for feed posts?
4:5 occupies more vertical space in the feed, so it's generally the better choice. 1:1 is the safer option when the same asset has to work across placements you don't control.

Should I put the aspect ratio in the prompt?
No — set it in the aspect ratio setting. A prompt describing "vertical" is a hint the model may ignore; the setting is the actual instruction. Then verify with ffprobe.

Where to go from here

Aspect ratio is the cheapest mistake to avoid and one of the more expensive ones to fix, because the fix is usually "generate it again". Decide where the clip is going before you generate it, set the ratio explicitly, and check the pixels before it enters your scheduler.

Looking for something else? Browse all 106 AI video guides in one list.

Looking for something else? Browse all 106 AI video guides in one list.

If you want to compare notes with people shipping short-form daily, that's what the AI Video Generator Skool community is for — real specs, real pipelines, and a heads-up when a platform changes what it accepts. Come and join us. If you'd rather skip the tooling entirely, we'll make it for you: custom AI-generated video.