How Long Should a Short-Form Video Be? Ideal Lengths for Shorts, TikTok, and Reels

Short answer: make one vertical video between 20 and 45 seconds and it will perform well on YouTube Shorts, TikTok, and Instagram Reels simultaneously. Here’s the platform-by-platform reasoning, and when to break the rule.

The limits vs the sweet spots

Every platform allows far more than what actually works. YouTube Shorts accepts up to 3 minutes; TikTok accepts up to 10 minutes from the app; Reels stretches similarly. But the maximums are not targets — short-form feeds reward completion rate, and completion rate collapses as videos get longer.

• YouTube Shorts: 15–60 seconds is the reliable zone. Shorts leans on search and suggested feeds, so a keyworded title plus a video short enough to loop does the ranking work.
• TikTok: 15–34 seconds. TikTok’s own creator guidance has repeatedly pointed at the low-20s-to-mid-30s range as the engagement sweet spot.
• Instagram Reels: 15–45 seconds. Reels rewards watch-through and shares; under 45 seconds keeps both high.

Why completion rate beats total watch time here

A 30-second video watched to the end signals “show this to more people” louder than a 3-minute video abandoned at 40%. Loops amplify this: a video short enough to watch twice registers >100% completion on TikTok and Reels, which is one of the strongest distribution signals available to a small account.

When longer is right

Tutorials, storytimes, and mini-vlogs can earn 60–180 seconds — but only when the format demands it and the first three seconds hook hard. If you’re cutting a longer video down, cut to the single strongest idea rather than compressing everything.

One length, every platform

The convenient truth: the sweet spots overlap. A 20–45 second vertical 9:16 MP4 is inside the ideal range for all four major platforms (Facebook included), which means one export serves everywhere — no per-platform re-editing. That’s the workflow Multiposter is built around: upload that one file, write one caption, and publish to YouTube Shorts, TikTok, Instagram Reels, and Facebook at once, with length and size limits validated per platform before anything goes live.

If you want the formatting details per pair of platforms — like caption style differences between Shorts and TikTok — see the Shorts-to-TikTok formatting comparison. And when your length is dialed in, cross-post it everywhere in about 30 seconds.