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How to Write Short-Form Video Prompts (TikTok / Reels / Shorts)

Short-form has its own visual grammar — vertical, fast, hook-driven. AI prompts need to match.

Published: Author: AI Productivity Guide Team 🌐 查看中文版本

What this tutorial solves

Short-form video has different rules than commercial. Vertical, fast cuts, attention hooks in first second. Prompts that ignore this make AI clips that flop on these platforms.

What’s different per platform

All four are 9:16 vertical, but the algorithm rewards different things, the native style is different, and the sweet-spot length is different. One prompt template for all of them underperforms on every one.

Douyin

  • Format: 9:16, 1080x1920. Length: 7-60s, 15s common.
  • Algorithm signals: completion rate dominates; replays + comments + shares matter; no native “save”.
  • Native style: heavy on-screen captions; fast cuts (0.5-1.5s); first-second hook is non-negotiable; trending sounds layered under voiceover.

TikTok

  • Format: 9:16, 1080x1920. Length: 15s most algorithm-friendly; up to 10min but rarely surfaced.
  • Algorithm signals: completion rate, shares, comment depth, hashtag follow. Niche FYP dominates.
  • Native: subtitles on by default; “first 2s = stop the scroll”; trending sounds; duet/stitch loops; creator-fund pulls toward 60s+ if monetizing.

Reels (Instagram)

  • Format: 9:16, 1080x1920. Length: up to 90s; 15-30s sweet spot.
  • Algorithm signals: shares + saves matter heavily; reach to non-followers; comment depth.
  • Native: looping clips (end visually matches start), aesthetic-forward color grading, brand-consistent palette, the cover frame matters (shows in feed grid).

Shorts (YouTube)

  • Format: 9:16, 1080x1920. Length: max 60s.
  • Algorithm signals: average view duration, swipe-away rate, subscribe-clicks-from-Short (YouTube optimizes for converting Shorts viewers to channel subscribers).
  • Native: more text on screen than IG; “tip-format” educational works well; often a teaser to long-form on the same channel.

Same topic “remote work” — prompted four different ways

Douyin:

9:16, 1080x1920, 15s. First frame: a cat sitting on an open laptop keyboard,
owner's hand reaches in to push it off and the cat glares.
Bold caption "Day 87 of remote work". 4 fast cuts: cat blocks screen, coffee
spills, takeout boxes on desk, person on a call from bed. Cut every 1s, last
frame loops back to the first. BGM: trending emotional sound.

TikTok:

9:16, 1080x1920, 15s. First 2s: a person stares into camera and says
"remote work isn't what you think", English caption burned in.
Mid: three contrast cuts (suit on top + pajama pants, bed = office,
2am answering email). End: punchline "but I'm never going back". Stitch-friendly.

Reels:

9:16, 1080x1920, 20s. Aesthetic-forward: natural light, beige + wood palette.
Open on a latte-art close-up, pull back to a desk with a MacBook. Three location
cuts: window seat, balcony, cafe. End frame matches the start frame (seamless loop).
Cover frame: latte art. BGM: lo-fi piano.

Shorts:

9:16, 1080x1920, 45s. Burned-in title "3 things nobody tells you about remote work".
Three ~12s segments, each opens with a big number caption. End with a direct
"full breakdown on my channel" pointing to a long-form video. Pace slightly faster than IG.

Who this is for

Short-video creators, social media managers, brands that need TikTok / Reels / Shorts content at scale.

When to reach for it

Weekly content batches, ad creative tests, content series, branded loops.

When this is NOT the right tool

Long-form YouTube; landscape video for desktop; cinematic ads where pacing is slower.

Step by step

  1. Aspect ratio: 9:16 portrait, always. Generating 16:9 then cropping wastes time.
  2. First-second hook: the opening frame must surprise or stop scroll. Prompt explicitly: “first frame: striking visual that pays off in seconds 2-5”.
  3. Pacing: clips should be 3-8 seconds. Longer = scroll loss.
  4. Motion: medium to high. Static clips lose in feeds.
  5. Subject in upper third: phone UI covers bottom for captions. Compose with that in mind.
  6. Loop-friendly: end frame should connect back to start frame if possible. “Loopable” prompts feel native.
  7. Generate 4-6 variants per shot. Pick the one with the strongest first second.

A series of 5 fitness reels: each prompt — 9:16, first-frame hook, single motion, 5s, subject upper third. Generate and edit into 30s reel with on-brand captions.

Common mistakes

  • Forgetting aspect ratio until after generation.
  • Slow openings. First second is the whole game on short-form.
  • Subject in center — phone caption overlay covers it.
  • Long single clips. Cut to multiple short ones.

Advanced tips

  • For ads, generate a set of 10 with the same product but different hooks. A/B test which hook converts.
  • Pair with trending music in the editor. Trending audio amplifies reach more than visual quality.
  • Save platform-specific prompt prefixes (“vertical 9:16, mobile-optimized, captions-safe lower third”).

Output checklist

  • 9:16 vertical aspect ratio.
  • First frame is a hook (striking, not generic).
  • Subject positioned for caption overlay.
  • Length 3-8 seconds per clip.
  • Motion present (medium+).

FAQ

  • Best tool for short-form?: Sora / Veo for prompt-following; Kling for accessibility. Test on your platform.
  • Will TikTok penalize AI video?: No explicit penalty currently. But check platform policy regularly — disclosure requirements vary.

Tags: #Tutorial #Video generation #Short video #Prompt

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