The short answer
Aspect ratio gets over-discussed and under-decided. For almost everyone the answer is one ratio, and the interesting part is knowing precisely when it stops being the answer.
The four ratios, and what each is for
| Ratio | Shape | Best for | Avoid for |
|---|---|---|---|
| 9:16 | Full-screen vertical | Reels, TikTok, Shorts, Stories, Threads | Long-form YouTube |
| 4:5 | Tall portrait | Instagram and Facebook feed posts | Anything full-screen |
| 1:1 | Square | Feed posts across mixed platforms; safe fallback | Short-form video feeds |
| 16:9 | Landscape | Long-form YouTube, desktop viewing | Reels, TikTok, Shorts |
Why vertical wins by default
It is not an aesthetic argument, it is a screen-space one. A 9:16 video fills a phone. A 16:9 video in the same feed occupies roughly a third of the height, with black bars above and below, competing against neighbours that fill the frame.
That difference shows up in the first second, which is the only second that decides whether someone keeps watching. Every short-form feed is built vertical-first, and posting landscape into one is a self-inflicted handicap.
When 4:5 beats both
For a feed post rather than a full-screen one, 4:5 is the quiet winner on Instagram and Facebook. It takes more vertical space than square, so it pushes competing posts further down the screen, while still being a feed-native shape rather than a full-screen takeover.
It is a small edge, and only worth the extra export if feed posts are a real part of what you do.
Getting it wrong produces no error
Worth stating plainly: an aspect-ratio mismatch is not usually a rejection. The platform crops or letterboxes and publishes anyway, so nothing tells you. That makes it the failure mode people repeat for months — covered in more detail in why your upload failed.
It is also why our scheduler surfaces ratio mismatches as a warning before a post is queued rather than staying silent about them. Length and file size block; framing is a judgement call you should at least be told about.
Questions people actually ask
What is the best aspect ratio for social media video?
9:16 vertical for short-form. It is native on Instagram Reels and Stories, TikTok, YouTube Shorts, Facebook Reels and Threads, and accepted on X, LinkedIn and Pinterest. Use 16:9 only for long-form YouTube.
Is 1:1 or 4:5 better for Instagram?
4:5 for feed posts — it occupies more vertical screen space than square while staying feed-native. 1:1 is a reasonable fallback when one file has to serve several platforms.
Can I post a landscape video to Reels?
You can, and it will publish, but it gets letterboxed into a strip in the middle of the phone screen with black bars around it. It is one of the most common reasons a repurposed video underperforms.
Do I need to export a different ratio per platform?
Usually not. One 9:16 export covers every short-form destination. A second export is only worth it for long-form YouTube in 16:9, or 4:5 if Instagram feed posts matter to you.