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EasingClassic eases

easeInOutQuart

It is slow at both ends and fast in the middle. A strong ease: most of the travel happens in the fast section.

easeInOutQuart reaches 50% of its travel at 50% of the time and 90% at 67%. Its peak speed is 4x the average.

Classic easesfamily: quartpeak 4x

Progress against time0100.51progress50%90%
The dashed line is linear. The dots mark 50% and 90% of the travel.
Velocity, in multiples of average speed01400.51speed, x average
The dashed line is 1x, the speed of linear.

Live demo

The blue box uses the exact linear() string below, in your browser. The grey box is linear.

easeInOutQuart
linear

Your system asks for reduced motion, so the boxes rest at the end of the move.

Numbers

50% of travel
50%of the time
90% of travel
67%of the time
After 10% of time
0.08%of the travel is done
Peak speed
4xtimes the average
Overshoot
0%stays inside the end
Undershoot
0%never below the start
linear() points
41at a 0.002 tolerance
cubic-bezier
closeworst gap 2.0 points

Copy the code

css linear() (exact)
animation-timing-function: linear(0, 0, 0.0001, 0.0003, 0.0008, 0.002, 0.0041, 0.0075, 0.0128, 0.0205, 0.0313, 0.0458, 0.0648, 0.0893, 0.12, 0.1582, 0.2048, 0.261, 0.3281, 0.4073, 0.5, 0.5927, 0.672, 0.739, 0.7952, 0.8418, 0.88, 0.9107, 0.9352, 0.9542, 0.9688, 0.9795, 0.9872, 0.9925, 0.996, 0.998, 0.9992, 0.9997, 1, 1, 1);
cubic-bezier (nearest fit)
animation-timing-function: cubic-bezier(0.77, 0, 0.23, 1);

Least-squares fit to the easeInOutQuart curve; the worst gap is 2.0 points of travel. It is close, not exact: use linear() when the end of the curve matters.

web animations api
el.animate({ translate: ['0 0', '240px 0'] }, { duration: 600, easing: 'linear(0, 0, 0.0001, 0.0003, 0.0008, 0.002, 0.0041, 0.0075, 0.0128, 0.0205, 0.0313, 0.0458, 0.0648, 0.0893, 0.12, 0.1582, 0.2048, 0.261, 0.3281, 0.4073, 0.5, 0.5927, 0.672, 0.739, 0.7952, 0.8418, 0.88, 0.9107, 0.9352, 0.9542, 0.9688, 0.9795, 0.9872, 0.9925, 0.996, 0.998, 0.9992, 0.9997, 1, 1, 1)', fill: 'both' });
vawe
import { easeInOutQuart } from '../../core/motion/curves.js';
import { curveToLinear } from '../../core/motion/springs.js';

const easing = curveToLinear(easeInOutQuart, { tolerance: 0.002 }); // the linear() string above
const x = easeInOutQuart(u);                                         // per-frame code, u in 0..1

When to use it, and when to avoid it

Use it for

  • Moves between two resting positions: camera pushes, slides and loops.
  • For quart: panels and overlays that need a clear stop.

Avoid it for

  • Quick UI feedback under 200 ms: the slow start delays the response.
  • For quart: short moves under 150 ms: the slow part is too short to see.

The nearest vawe ease

The closest of the nine vawe After Effects eases is swap, an RMS gap of 0.0134 in progress. After Effects and vawe set the shape with two handles, so it can be tuned where a named curve cannot.