AI video sizes for TikTok, Reels, Shorts and YouTube

Why aspect ratio decides reach

Every feed reserves a shape for its videos. Post a wide clip into a vertical feed and it either shrinks into a small box or gets cropped, losing the edges of the frame. Post a tall clip into a landscape player and you get black bars on both sides.

Both outcomes look accidental, and they cost you the first second — the moment when a viewer decides whether to keep watching. Matching your export to the platform is not a technicality; it is part of the creative work.

The three formats every trend can render

Rather than juggling a dozen platform-specific resolutions, AI Gen Video renders three canonical aspect ratios. Pick the one that matches your destination and the rest follows.

• 9:16 — vertical, for TikTok, Instagram Reels, YouTube Shorts and Stories.
• 1:1 — square, for feed posts and cross-posting to mixed feeds.
• 16:9 — landscape, for YouTube, embedded players and widescreen displays.

Not every template offers all three ratios. Where a trend is locked to one shape, only that option will appear in the format selector.

Vertical 9:16: TikTok, Reels and Shorts

Vertical is the default language of short-form video. TikTok, Instagram Reels and YouTube Shorts all present 9:16 full-screen, and it is the shape that fills the most of a phone display — which is exactly what these feeds reward.

If your goal is discovery through short-form feeds, render 9:16. It is the format that trend clips are built for: one clear action, centred, filling the frame from top to bottom.

Square 1:1: feed posts and cross-posting

Square sits between the two extremes. It is the safest cross-platform shape because it survives cropping into both vertical and horizontal feeds without losing much.

Use 1:1 when you want one file to work in several places, or when you are posting into a grid-style feed where consistency matters more than filling the screen. It is the versatile middle option.

Landscape 16:9: YouTube and embeds

Landscape is the shape of traditional video players. YouTube, embedded players and most desktop viewing contexts expect 16:9, so a wide render sits naturally without letterboxing.

Choose 16:9 when the clip is meant to be watched on a larger screen, embedded on a site, or slot into a landscape playlist rather than a scrolling feed.

Safe zones, captions and UI overlap

Feeds overlay their own interface on top of your video: captions, usernames, buttons and progress bars. On a vertical clip, the bottom and top edges are often covered by this chrome, so important parts of a scene should sit towards the centre.

Keep the main action roughly in the middle of the frame and leave the edges as breathing room. Because trend clips are generated centred by default, this usually takes care of itself — but it is worth checking the result before posting, especially if a scene has detail near the frame edges.

Picking a format per trend

Some trends naturally suit one shape. A two-person walk through a lobby reads well in landscape or square, where both subjects fit comfortably side by side. A single-subject clip tends to shine in vertical, where the subject fills the frame.

If you are unsure, match the format to the platform first and the trend second — the platform decides how the clip is seen, and the trend just decides what happens inside it.

Re-exporting the same video for another platform

You do not have to choose one destination forever. If a clip performs well in one place, render the same trend at another aspect ratio and post it where it fits. A vertical hit can often become a landscape post for a different audience.

Keep the quality tier sensible for each platform: the entry tier — 768P on MiniMax H3, 720P on Seedance 2.5 — is usually enough for a phone feed, while the top tier is worth it for a larger screen or a hero placement.

Aspect ratio vs. resolution

These two things are often confused, but they control different parts of the result. Aspect ratio is the shape of the frame — 9:16, 1:1 or 16:9 — and it decides whether the clip fits a feed without cropping or letterboxing. Resolution is how many pixels fill that shape — 720P class up to 2K, depending on the model — and it decides how crisp the image looks.

Changing the aspect ratio changes where the video fits; changing the resolution changes how sharp it looks in that place. For a phone feed, the shape matters more than the pixel count, which is why it is usually better to pick the right ratio at 720P than the wrong ratio at 1080P.

Only the resolution tier affects the credit cost. Switching between 9:16, 1:1 and 16:9 is free.

A quick decision guide

If you only remember one thing from this guide, make it this short set of rules.

• Posting to TikTok, Reels or Shorts → 9:16.
• Posting one clip across several networks → 1:1.
• Posting to YouTube or embedding on a site → 16:9.
• Testing whether a photo and trend pair well → any ratio at the entry resolution tier, then re-render the winner.

Beyond the big four

The same three shapes cover almost everything else. Instagram Stories and Pinterest both favour vertical 9:16; LinkedIn and X feeds tolerate square or landscape; most website embeds and internal players expect 16:9.

When a platform is not on your list, work backwards from how people watch it. If they watch on a phone held upright, choose vertical. If they watch in a wide player on a desktop, choose landscape. Square is the safe middle when you genuinely cannot tell.

Reframing a clip you already have

If you already posted a clip in one shape and want it in another, the cleanest route is to re-generate it at the new aspect ratio rather than cropping the existing file. Rendering the trend again gives the model a chance to compose the scene for the new frame, instead of forcing a vertical shot into a horizontal one.

Cropping an existing video is possible, but every crop throws away part of the image. A wide clip cropped to vertical loses its left and right edges, which is often exactly where the interesting detail sits. Re-generating is the better trade whenever you still have the original photo.

Changing the aspect ratio costs nothing extra — only the quality tier affects the credit price.

Preview before you post

Before publishing, watch the clip in the shape and size it will actually appear. A video that looks great full-screen on a laptop can lose its subject behind a phone feed’s interface when viewed vertically, and a detail that reads clearly on a large screen can vanish on a small one.

The last check is the frame edges: make sure the main action sits comfortably inside the middle of the frame, with the outer edges treated as breathing room that the platform’s interface is allowed to cover.

A short posting checklist

Five quick checks before a clip goes live — they take a minute and prevent most of the avoidable mistakes.

• Pick the ratio that matches the destination feed, not the one you generated last time.
• Preview in the true shape and size before you publish.
• Keep the main action centred so captions and buttons do not cover it.
• Match the quality tier to the screen: the entry tier for a phone feed, the top tier for a large display or hero placement.
• Keep the original photo around, so you can re-render at another ratio later without starting over.

Get these right and the same clip travels further, looking deliberate everywhere you post it rather than accidental in most places.