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EasingClassic eases

easeInOutExpo

It is slow at both ends and fast in the middle. An extreme ease: the speed changes by orders of magnitude, so one tenth of the time carries most of the travel.

easeInOutExpo reaches 50% of its travel at 50% of the time and 90% at 62%. Its peak speed is 6.92x the average.

Classic easesfamily: expopeak 6.92x

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.

easeInOutExpo
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
62%of the time
After 10% of time
0.2%of the travel is done
Peak speed
6.92xtimes the average
Overshoot
0%stays inside the end
Undershoot
0%never below the start
linear() points
81at a 0.002 tolerance
cubic-bezier
closeworst gap 3.6 points

Copy the code

css linear() (exact)
animation-timing-function: linear(0, 0.0006, 0.0007, 0.0008, 0.001, 0.0012, 0.0014, 0.0016, 0.002, 0.0023, 0.0028, 0.0033, 0.0039, 0.0046, 0.0055, 0.0066, 0.0078, 0.0093, 0.011, 0.0131, 0.0156, 0.0186, 0.0221, 0.0263, 0.0313, 0.0372, 0.0442, 0.0526, 0.0625, 0.0743, 0.0884, 0.1051, 0.125, 0.1487, 0.1768, 0.2102, 0.25, 0.2973, 0.3536, 0.4204, 0.5, 0.5796, 0.6464, 0.7027, 0.75, 0.7898, 0.8232, 0.8513, 0.875, 0.8949, 0.9116, 0.9257, 0.9375, 0.9474, 0.9558, 0.9628, 0.9688, 0.9737, 0.9779, 0.9814, 0.9844, 0.9869, 0.989, 0.9907, 0.9922, 0.9934, 0.9945, 0.9954, 0.9961, 0.9967, 0.9972, 0.9977, 0.998, 0.9984, 0.9986, 0.9988, 0.999, 0.9992, 0.9993, 0.9994, 1);
cubic-bezier (nearest fit)
animation-timing-function: cubic-bezier(0.9, 0, 0.1, 1);

Least-squares fit to the easeInOutExpo curve; the worst gap is 3.6 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, 0.0006, 0.0007, 0.0008, 0.001, 0.0012, 0.0014, 0.0016, 0.002, 0.0023, 0.0028, 0.0033, 0.0039, 0.0046, 0.0055, 0.0066, 0.0078, 0.0093, 0.011, 0.0131, 0.0156, 0.0186, 0.0221, 0.0263, 0.0313, 0.0372, 0.0442, 0.0526, 0.0625, 0.0743, 0.0884, 0.1051, 0.125, 0.1487, 0.1768, 0.2102, 0.25, 0.2973, 0.3536, 0.4204, 0.5, 0.5796, 0.6464, 0.7027, 0.75, 0.7898, 0.8232, 0.8513, 0.875, 0.8949, 0.9116, 0.9257, 0.9375, 0.9474, 0.9558, 0.9628, 0.9688, 0.9737, 0.9779, 0.9814, 0.9844, 0.9869, 0.989, 0.9907, 0.9922, 0.9934, 0.9945, 0.9954, 0.9961, 0.9967, 0.9972, 0.9977, 0.998, 0.9984, 0.9986, 0.9988, 0.999, 0.9992, 0.9993, 0.9994, 1)', fill: 'both' });
vawe
import { easeInOutExpo } from '../../core/motion/curves.js';
import { curveToLinear } from '../../core/motion/springs.js';

const easing = curveToLinear(easeInOutExpo, { tolerance: 0.002 }); // the linear() string above
const x = easeInOutExpo(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 expo: a title or number that must snap in and then rest.

Avoid it for

  • Quick UI feedback under 200 ms: the slow start delays the response.
  • For expo: anything the viewer must follow with the eye: the fast section is too short to track.

The nearest vawe ease

The closest of the nine vawe After Effects eases is swap, an RMS gap of 0.0473 in progress. After Effects and vawe set the shape with two handles, so it can be tuned where a named curve cannot.