Guides · 08

Performance and playback

How Animated avoids work each frame, how to check which path an element uses, and how the numbers on the home page were measured.

Three playback paths

Animated picks a path per property. The API does not change with the path.

Path	When	Work per frame
browser	Finite transform and opacity motion on `Animated.<tag>` elements, including springs	None in the page's JavaScript
css	Exact curves the browser can express with shared CSS keyframes	None in the page's JavaScript
js	Ordinary style variables, input, custom computation and sequence boundaries	One write per value, no React render

One value, many elements

Derivations of a hook value are calc() expressions. With scope, one variable write per frame drives every element in the container.

Preparing the example…

JavaScript is off. The code below is the complete example.

App.jsx

import { useRef } from 'react';
import { Easing, loop, timing, useAnimated } from '@kkwaenggwari/animated';
import './styles.css';

export default function App({ count = 1600, amplitude = 16, duration = 2400 }) {
  const field = useRef(null);
  const renders = useRef(0);
  renders.current += 1;

  // Written once per frame on the field; every dot derives from it in CSS.
  const wave = useAnimated(
    0,
    (value) => {
      loop(timing(value, { toValue: 1, duration, easing: Easing.linear }));
    },
    [duration],
    { scope: field },
  );

  const columns = Math.ceil(Math.sqrt(count * 2.8));
  const dots = Array.from({ length: count }, (_, index) => index);

  return (
    <div className="stage">
      <div className="meta">
        <span>{count.toLocaleString('en-US')} dots</span>
        <span>React renders: {renders.current}</span>
      </div>
      <div className="field" ref={field} style={{ gridTemplateColumns: `repeat(${columns}, 1fr)` }}>
        {dots.map((index) => {
          const phase = (index % columns) / columns + Math.floor(index / columns) / 18;
          return (
            <i
              key={index}
              style={{
                transform: `translateY(calc(sin((${wave} + ${phase}) * 1turn) * ${amplitude}px))`,
                opacity: `calc(0.55 + cos((${wave} + ${phase}) * 1turn) * 0.45)`,
              }}
            />
          );
        })}
      </div>
    </div>
  );
}

styles.css

.stage {
  display: grid;
  gap: 16px;
  padding: 24px;
}

.meta {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 8px;
  font:
    600 14px/1.4 ui-monospace,
    SFMono-Regular,
    Consolas,
    monospace;
  color: #1a33c7;
}

.field {
  display: grid;
  grid-auto-rows: 1fr;
  gap: 2px;
  height: 280px;
  padding: 28px 16px;
  border-radius: 16px;
  background: #0b1440;
  overflow: hidden;
}

.field i {
  display: block;
  width: 100%;
  max-width: 8px;
  aspect-ratio: 1;
  align-self: center;
  justify-self: center;
  border-radius: 50%;
  background: #5c7cff;
}

.field i:nth-child(3n) {
  background: #8fb0ff;
}

.field i:nth-child(7n) {
  background: #ffffff;
}

Check the path

inspect(element) returns the driver and fallback reason for each animated property during a real run.

debug.js

import { inspect } from '@kkwaenggwari/animated';

console.table(inspect(element));
// property   driver     reason
// transform  browser    null
// opacity    css        null
// --level    js         css-variable-requires-js

Starts from the first frame

When the task that starts a motion keeps the main thread busy, such as hydration or a large commit, the motion restarts once that work ends instead of appearing already advanced. A start on a hidden page finishes in the background.

How the home page numbers were measured

Each scenario ran in a fresh page after one warm-up, three recorded samples, reporting the median. JavaScript time is the time spent inside animation-frame callbacks while the motion runs. It excludes style, layout and paint, which the browser does for every approach, so it is not a measure of total CPU or frame rate.

Browser playback does not make layout, paint, compositing or memory free. Measure the real screen on the devices you support.

Scenario	Setup	Result
400 Animated.div elements move translateX and fade in (timing, 1800 ms)	seed/pose/tempo on Animated.div; 800 browser animations	0.00 ms
One useAnimated value drives 10,000 elements in ordinary style (loop, 1200 ms)	transform and opacity as calc() of one CSS variable written on a scope element	0.13 ms

2026-09-28 · Chrome 153.0.8010.52 (headless) · Windows_NT x64 · Intel(R) Core(TM) i7-14700K