If you post the same video on Instagram, YouTube and TikTok, you have felt the problem: each app wants something slightly different. The good news is that the shape of the video is the same everywhere. What changes is length, captions and where the app's buttons cover your picture.
The specs at a glance
| Platform | Aspect ratio | Resolution | Length |
|---|---|---|---|
| Instagram Reels | 9:16 | 1080 x 1920 | Sources report ceilings from 3 to 20 minutes, depending on account and rollout |
| YouTube Shorts | 9:16 | 1080 x 1920 | Up to 3 minutes in several 2026 guides |
| TikTok | 9:16 | 1080 x 1920 | TikTok's ad specs list 10 minutes, 500 MB and at least 516 kbps for in-feed ads. In-app limits differ |
The shared ground is narrow but solid: vertical 9:16, 1080 x 1920, H.264 video and AAC audio. A 30 to 60 second export at that size usually stays well under every published file-size limit.
How long should a short video be?
Treat the maximum as what is technically allowed, not what to aim for. Platform guidance and observed performance both point well below the ceilings. For cross-posting, 15 to 60 seconds works across all three. The average initial view on Reels is reported to be around three seconds, so the opening matters more than the total length.
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Get a quote How Motex worksCaptions and safe zones
YouTube accepts a separate subtitle file (.srt or .vtt) that viewers can switch on and off. Reels and TikTok work best with captions burned into the picture, because their auto-captions can mangle product names and technical terms. No provider publishes binding safe-zone measurements, so keep captions and logos away from the top, bottom and right edges where buttons and titles sit, and check on a real phone.
Editor's export checklist
- Build the timeline at 1080 x 1920, 9:16, at the frame rate of your footage.
- Put the hook in the first second or two. Do not open with a logo.
- Export H.264 MP4 with AAC audio.
- Keep one clean master without captions, plus a captioned version for Reels and TikTok.
- Export an .srt for YouTube.
- Trim to the shortest length that still tells the story.
- Play the file on a phone before you upload.
Common mistakes
- Uploading horizontal 16:9 footage and letting the app add black bars.
- Putting text where the app's buttons and captions will cover it.
- Exporting at low resolution because the preview looked fine on a laptop.
- Making a different cut for each platform when one master would do.