Remotion (Programmatic Video)

Build real MP4/GIF/WebM videos in React. Every frame is a pure function of useCurrentFrame(), so output is deterministic, scrubbable, diffable, and renderable in CI. The code-first alternative to After Effects for templated and data-driven motion graphics.

When to use

Render MP4/GIF/WebM from code (social clips, title cards, explainers).
Templated/data-driven videos: one composition, many outputs from props (per-user, per-record, per-row of a CSV/DB).
Motion graphics that must be versioned, code-reviewed, and rendered in CI without a GUI.
Programmatic audio sync, charts that animate from data, or embedding shaders/Three.js into video.

Core techniques

Frame-driven animation

Animation is derived from the current frame, never from setState or requestAnimationFrame. interpolate maps an input range to an output range; spring produces physically natural motion.

import {useCurrentFrame, useVideoConfig, interpolate, spring} from 'remotion';

export const Title = () => {
  const frame = useCurrentFrame();
  const {fps} = useVideoConfig();

  // Fade in over frames 0-30, then stay (clamp prevents over/undershoot).
  const opacity = interpolate(frame, [0, 30], [0, 1], {
    extrapolateLeft: 'clamp',
    extrapolateRight: 'clamp',
  });

  // Spring entrance; divide by spring duration is unnecessary — drive transforms directly.
  const scale = spring({frame, fps, config: {damping: 200, mass: 1, stiffness: 100}});

  return <h1 style={{opacity, transform: `scale(${scale})`}}>Hello</h1>;
};

Always clamp interpolate unless an intentional overshoot is desired — by default it extrapolates linearly past the range, which produces opacity > 1 or negative values.

Scheduling: Sequence and Series

<Sequence> shifts time: children see frame reset to 0 at the sequence's from. Use it to place clips on a timeline. <Series> lays out back-to-back segments without manual offset math.

import {Sequence, Series, AbsoluteFill} from 'remotion';

export const Timeline = () => (
  <AbsoluteFill style={{backgroundColor: 'black'}}>
    <Sequence from={0} durationInFrames={60}><Intro /></Sequence>
    <Sequence from={60} durationInFrames={90}><Body /></Sequence>

    {/* Series auto-sequences; offset overlaps the previous segment for crossfades */}
    <Series>
      <Series.Sequence durationInFrames={60}><ShotA /></Series.Sequence>
      <Series.Sequence durationInFrames={60} offset={-15}><ShotB /></Series.Sequence>
    </Series>
  </AbsoluteFill>
);

Composition registration + parametric props

The <Composition> declares id, size, fps, duration, and defaultProps. A zod schema makes props type-safe and editable in the Studio sidebar.

import {Composition} from 'remotion';
import {z} from 'zod';

export const schema = z.object({
  title: z.string(),
  accent: z.string(),
  fps: z.number().default(30),
});

export const Root = () => (
  <Composition
    id="Promo"
    component={Promo}
    durationInFrames={150}
    fps={30}
    width={1080}
    height={1920}
    schema={schema}
    defaultProps={{title: 'Launch', accent: '#5b8cff', fps: 30}}
  />
);

To make duration data-dependent, use calculateMetadata on the Composition to compute durationInFrames from props (e.g. number of rows × frames per row) before render.

Audio and beat sync

import {Audio, staticFile, useCurrentFrame, useVideoConfig} from 'remotion';

const BEATS_SEC = [0.5, 1.0, 1.5, 2.0]; // detected offline
export const Music = ({children}) => {
  const frame = useCurrentFrame();
  const {fps} = useVideoConfig();
  const t = frame / fps;
  const onBeat = BEATS_SEC.some((b) => Math.abs(t - b) < 1 / fps);
  return (
    <>
      <Audio src={staticFile('track.mp3')} />
      <div style={{transform: `scale(${onBeat ? 1.06 : 1})`}}>{children}</div>
    </>
  );
};

Detect beats offline (e.g. with web-audio-beat-detector or aubio) and bake the timestamps into props — never analyze audio at render time, since headless rendering has no realtime audio clock.

Rendering

Preview in the browser-based Studio; render headlessly via CLI or the programmatic API.

npx remotion studio                                  # interactive preview
npx remotion render Promo out/promo.mp4 \
  --props='{"title":"Launch","accent":"#f43"}'        # pass parametric props
npx remotion render Promo out.gif --codec=gif         # GIF output

For batch/data-driven pipelines, render in Node with @remotion/renderer (bundle once, render many) — see the reference file.

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.

Remotion is frame-deterministic by construction — every frame is a pure function of useCurrentFrame(), so you can render any exact frame headlessly with no seek harness (this is the heavy-tier counterpart to a web scene's ?t=N). Use this tier when the output must be an MP4/GIF, must carry exact numbers/text, or batches from data; for a lightweight web animation, deliver standalone HTML instead.

Output contract:

A Remotion project with the composition registered (<Composition> + zod schema + defaultProps), all motion frame-driven (no timers / Date.now() / Math.random()).
Deliverable = the rendered out/*.mp4 (plus the project, so the user can re-render with new props/data).
Duration data-dependent? compute it in calculateMetadata, not by hand.

Verify loop — render stills → inspect → encode. Render single frames first (cheap, no video encode), inspect them, and encode the full video only once the frames are right.

# 1. Frame-exact stills at start / mid / end (PNG, headless, fast)
npx remotion still Promo out/f-start.png --frame=0
npx remotion still Promo out/f-mid.png   --frame=75
npx remotion still Promo out/f-end.png   --frame=149   # last frame = durationInFrames - 1
#    render with the SAME props you'll ship, not just defaultProps:
#    npx remotion still Promo out/f-mid.png --frame=75 --props='{"title":"Launch"}'

# 2. Inspect each PNG — fidelity (matches brief; numbers/text correct) AND
#    artifacts (text overflow, off-canvas, clipped safe-area, missing font, wrong data binding).

# 3. Only after the stills check out, encode the video:
npx remotion render Promo out/promo.mp4 --props='{"title":"Launch"}'

Use npx remotion compositions to read each composition's durationInFrames/fps and pick the end frame.
Data-driven / batch: verify ONE representative props set via stills before batch-rendering all rows — catch a layout bug once instead of N times.
README demo GIF for free: npx remotion render Promo out/demo.gif --codec=gif produces the first-screen proof clip (Direction D).

Before you finish:

npx remotion still renders cleanly at frame 0, mid, and last — no errors, no missing assets/fonts.
Numbers/text are exact and inside safe areas at every checked frame.
Frame-driven only — no Date.now() / Math.random() / timers (determinism holds in CI).
Props are zod-typed; the shipped props render correctly (not just defaultProps).
Full MP4 encoded and plays; (optional) GIF rendered for the README.

Quick reference

Need	Use
Map time → value	`interpolate(frame, [a,b], [x,y], {extrapolateRight:'clamp'})`
Natural easing	`spring({frame, fps, config})`
Place a clip at t	`<Sequence from durationInFrames>`
Back-to-back shots	`<Series>`
Audio	`<Audio src={staticFile(...)} />`
Frame ↔ seconds	`frame / fps`
Loop a value	`frame % period` then interpolate
Editable props	zod `schema` on `<Composition>`
CI render	`npx remotion render` or `@remotion/renderer`

Gotchas

Never use Math.random(), Date.now(), or animation timers — they break determinism. Use random(seed) from Remotion for stable per-frame randomness.
Load fonts and assets via staticFile() and wait with delayRender/continueRender, or fonts pop in mid-render.
Default interpolate extrapolates — clamp it.
useCurrentFrame inside a <Sequence> is local (starts at 0); use useVideoConfig().durationInFrames for absolute timing.

Reference files

references/api-and-patterns.md — interpolate options and Easing, spring config recipes, Sequence/Series scheduling, <Audio> + beat-sync, parametric defaultProps with zod + calculateMetadata, CLI flags, programmatic @remotion/renderer batch rendering, and embedding GLSL shaders / Three.js (@remotion/three).

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SKILL.md