Short Form Video

Short-Form Video

Engineer a 9:16 video that survives the swipe. Short-form is not a small launch film — it is a retention machine: a hook that earns the first second, pattern interrupts that reset attention every few seconds, and often a loop that buys watch-time past 100%. The craft is timing, not polish.

When to use

• Reels / TikTok / YouTube Shorts (7–60s, vertical 9:16).
• Retention editing: fixing drop-off, adding pattern interrupts, tightening pacing.
• Hooks, seamless loops, repeatable short-form templates (one design, many topics).

Story structure (the retention contract)

Short-form storytelling is a contract with the viewer's thumb: every second must re-earn the next one. The narrative is shaped backwards from the retention curve, not forwards from an intro. Lock these before touching the timeline.

• One idea per video. A short carries exactly one payoff. A second idea splits attention and the curve sags in the middle — make it a second video instead. If you can't name the single takeaway in a sentence, you don't have a short yet.
• Open a loop in the first ~3s, close it last. The hook poses a question or gap (the open loop); the payoff answers it. The viewer stays because the loop is open — so never answer it early, and never bury the payoff under setup.
• No dead air. Every beat either advances the idea or resets attention. Cut anything that does neither. Silence, slow ramps, throat-clearing intros ("hey guys, in this video…") are where viewers swipe.
• Why the curve, not the cut, is the unit of work. The algorithm distributes whatever holds the per-second retention curve flat; a "good" edit that flattens the curve loses to an ugly one that keeps it up. You are editing the curve, and the hook gates everything after it — fix it first.

The narrative spine (the Hook → Setup → Body → Payoff/loop arc is budgeted in the table below):

| Move | Story job | Failure if missed | |---|---|---| | Hook | Open the loop; promise the payoff | Swipe in first 3s | | Tension hold | Keep the gap open through the body | Flat middle, mid-drop | | Payoff | Close the loop — the one idea, delivered | "Wasted my time," no share | | Loop / CTA | Feed back to frame 0, or one clear ask | No re-watch, no action |

(The retention arc table below assigns seconds to each move; this section is the narrative logic and ordering behind it. Hook grammar lists the hook archetypes.)

The one metric that drives everything

Retention, not production value. The algorithm distributes whatever holds viewers; ~87% decide to stay or swipe inside 3 seconds, and the threshold for distribution sits near 70%+ average view-through (Shorts ~73%, TikTok ~78%, Reels ~65%). Every decision below trades against that curve. A flawless shot that bores at 0:04 loses to an ugly one that holds.

The retention arc

| Beat | Job | Budget (of a 20s short) | |---|---|---| | Hook (0–1s) | One frame + one line that creates an open loop | 0–1s | | Setup | Pay off why watch — promise, stakes, or the gap | 1–4s | | Body | Deliver value in beats; one idea per beat | 4–17s | | Payoff / loop | Close the loop — or feed it back to frame 0 | 17–20s |

Scale the body, never the hook. A 60s short has a longer body and more beats — the same 1-second hook.

Hook grammar (first ~1s)

The hook is a sentence + a visual that opens a curiosity gap the brain needs closed. Pick one pattern and commit:

| Hook type | Shape | Best for | |---|---|---| | Open loop | "The reason your X keeps Y…" (answer delayed) | most content | | Direct promise | "3 ways to ___ in 30 seconds" | educational / listicle | | Pattern interrupt | snap-zoom / whip-pan / visual mismatch in frame 1 | entertainment | | Negation | "Stop doing ___" / "You're ___ wrong" | strong opinions |

Two rules: the hook line is on-screen as text by frame 1 (85% watch muted), and the most striking visual is also the first frame — never a slow ramp-in. Hold a strong opening frame; do not fade up from black.

Pattern interrupts & cut rhythm

A pattern interrupt is any change that resets attention: a hard cut, zoom punch, b-roll insert, sound effect, caption pop, or angle change. In short-form, density is high — a visual change every ~2–4 seconds; videos with an interrupt roughly every 4s hold ~58% vs ~41% for a static talking head. The killer is a flat middle: TikTok throttles distribution when the watch-through curve flattens, so never stitch the body from low-energy takes.

// Drive every interrupt off the FRAME, not wall-clock — renders deterministically.
import { useCurrentFrame } from "remotion";
const fps = 30;
const cuts = [0, 1.2, 3.0, 5.4, 8.0, 11.2, 14.0]; // seconds — uneven on purpose
const frame = useCurrentFrame();
const shot = cuts.findIndex((t, i) => frame  {
  const frame = useCurrentFrame(); const { fps } = useVideoConfig();
  const s = spring({ frame: frame - at * fps, fps, config: { damping: 12, stiffness: 200 } });
  const scale = interpolate(s, [0, 1], [1, 1.12]); // snap to 112% on the beat
  return {children};
};

Captions

Most viewers watch muted, so on-screen captions are not optional — they carry the content and double as a pattern interrupt when each phrase pops in. Keep 4–7 words per line, high contrast, inside the safe area. Do not re-implement caption animation here — use the caption-animation skill for word-by-word timing, karaoke highlight, and styling; this skill only places captions on the retention timeline and inside the 9:16 safe zone.

Loops & re-watch

A seamless loop counts each re-watch as fresh watch-time — a clean 8s loop watched 3× is 300% view-through, the strongest possible signal. Two techniques: match the last frame to the first (same composition, position, color) so the cut is invisible, and write a sentence loop — phrase the hook so the payoff feeds back into frame 0 ("…and that's why I never — " → loops to the start). Best length for re-watch is ~7–15s.

9:16 safe areas

Compose inside the universal safe zone so platform UI never covers text or faces.

| Zone | Pixels (1080×1920) | Avoid | |---|---|---| | Universal safe (all platforms) | center 900×1400 | anything critical outside it | | Top | keep clear ~120px | profile / sound UI | | Bottom | keep clear ~320px | captions, CTA, hashtags, audio bar | | Right | keep clear ~120px | like / comment / share rail |

Put the hook text and key subject in the center 900×1400 box. Reserve the bottom ~320px even if it looks empty in the editor — that is where the platform paints its own captions and buttons.

Output checklist

• Hook line is on-screen text by frame 1; strongest visual is the first frame (no fade-up).
• One open loop / promise set in the first ~4s.
• A visual pattern interrupt every ~2–4s; intervals uneven; no flat middle.
• Captions present (via caption-animation), 4–7 words, inside safe area.
• Loop closed — matched first/last frame or a sentence that feeds frame 0.
• Composed inside the 900×1400 center box; bottom 320px / top 120px / right 120px kept clear.
• Every animated value derived from useCurrentFrame() — no CSS/library timers.

Deliver & verify (rendered stills → MP4)

> Packaged helper (scripts/): tile your stills with scripts/contact-sheet.sh sheet.png f-hook.png f-mid.png f-end.png, then assert the encode with scripts/probe-mp4.sh out.mp4 [WxH] [fps]. See scripts/README.md.

The short ships as a Remotion composition (` + zod schema + defaultProps) — every cut, punch-in, and interrupt driven by useCurrentFrame(), never Date.now() / Math.random() / timers. Deliverable = out/*.mp4` + the project (re-render per topic). 9:16 vertical (1080×1920) is the default.

Verify loop — render stills → inspect → encode. Three frames test the three things that make or break retention: the hook, the pacing, and the loop seam.

# Stills at hook / mid-body / last frame — WITH SHIPPED PROPS (the real topic, not defaults)
npx remotion still Short out/f-hook.png --frame=10  --props='{"topic":"...","hook":"..."}'   # ~first 3s reads instantly
npx remotion still Short out/f-mid.png  --frame=N   --props='{"topic":"...","hook":"..."}'
npx remotion still Short out/f-end.png  --frame=L   --props='{"topic":"...","hook":"..."}'   # L = durationInFrames-1

# Inspect each PNG:
#  - HOOK frame (~frame 0-ish / first 3s): hook line is on-screen text and reads instantly; strongest visual already up (no fade-up)
#  - LOOP seam: compare f-hook(frame 0) vs f-end(last frame) — same composition/position/color for an invisible loop cut
#  - 9:16 safe area: hook + key subject inside the center 900x1400 box; clear of top ~12%, bottom ~20-35% (captions/CTA/audio), right action rail

npx remotion render Short out/short.mp4 --props='{"topic":"...","hook":"..."}'   # encode once stills verify
npx remotion render Short out/demo.gif --codec=gif                                # README proof clip

Per topic / batch: verify ONE topic via stills before rendering all of them. Use npx remotion compositions for durationInFrames/fps to pick the mid + last frames.

Before you finish:

1. Stills render cleanly at the hook, mid, and last frame — no errors.
2. The hook frame reads instantly (on-screen text + strongest visual up front, no fade-up); first vs last frame match for a clean loop seam.
3. Hook + subject + captions sit inside the 9:16 center 900×1400 safe box at every checked frame.
4. Frame-driven only — no Date.now() / Math.random() / timers; cuts uneven, no flat middle.
5. A real topic's shipped props (not defaultProps) render correctly; MP4 encoded, GIF optional.

Reference files

• references/retention-pacing.md — a complete runnable Remotion `` composition: a frame-driven shot scheduler with uneven cuts, the PunchIn pattern interrupt, an on-screen hook, a 9:16 safe-area overlay, and a seamless first/last-frame loop. Plus a hook-pattern library, a retention-curve debugging method, per-platform safe-zone maps, and the template×topic batch-render pattern.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: iart-ai
• Source: iart-ai/tiktok-video-skills
• License: MIT
• Homepage: https://www.iart.ai

Install and usage instructions live in the source repository linked above.