The ideal short-form video length isn't one number — it's three

TikTok's sweet spot in 2026 sits around 21-34 seconds — long enough for a real beat, short enough that most viewers finish it. Instagram Reels leans slightly shorter, with the algorithm favoring clips in the 15-30 second range. YouTube Shorts skews longer still, with 30-45 seconds giving enough room to demonstrate a point before the Shorts feed's faster scroll behavior kicks in.

The common instinct is to cut one length and export it everywhere. That's the easy path, but it quietly under-optimizes every platform except the one you cut for first.

The more important principle underneath all three numbers: completion rate beats length every time. A 45-second clip that 70% of viewers finish will outperform a 15-second clip only 40% of viewers sit through — length is a proxy for 'can this realistically hold attention,' not a target to hit for its own sake.

This is the case for per-platform export presets instead of one-size cuts. OptimaClip reformats a single source clip into platform-tuned lengths and aspect ratios in one pass, so the TikTok version and the Shorts version of the same moment aren't just resized — they're actually cut to each platform's real sweet spot.