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Easings (cubic-bezier timing functions) as custom properties and SCSS variables.


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easings.scss adds a set of CSS cubic-bezier timing functions (also named easings) as Custom Properties.

This library brings:

  • a set of easings (and their reversed version!) as CSS custom properties and SASS variables;
  • lighter generated CSS;
  • a shorter cubic-bezier() syntax;
  • reversed bezier curves with reverse-bezier();
  • code portability: same syntax as similar libraries.

⚠️ easings.scss version 1.x is compatible with Dart SASS while version 0.x sticks to node-sass. If you’re not sure about your environment, start with the installation section. The installation step is the only usage difference between both versions, but if you prefer to only read the documentation for 0.x, see v0.3.1 documentation.


Easings list

If you’re familiar with Bourbon’s easings, they are exactly the same. (Other visualization).

easing in-out in out
Sine $ease-in-out-sine $ease-in-sine $ease-out-sine
Quad $ease-in-out-quad $ease-in-quad $ease-out-quad
Cubic $ease-in-out-cubic $ease-in-cubic $ease-out-cubic
Quart $ease-in-out-quart $ease-in-quart $ease-out-quart
Quint $ease-in-out-quint $ease-in-quint $ease-out-quint
Expo $ease-in-out-expo $ease-in-expo $ease-out-expo
Circ $ease-in-out-circ $ease-in-circ $ease-out-circ
Back $ease-in-out-back $ease-in-back $ease-out-back

Aliases for a shorter syntax (not available in Bourbon):

easing in-out in out
Sine $in-out-sine $in-sine $out-sine
Quad $in-out-quad $in-quad $out-quad
Cubic $in-out-cubic $in-cubic $out-cubic
Quart $in-out-quart $in-quart $out-quart
Quint $in-out-quint $in-quint $out-quint
Expo $in-out-expo $in-expo $out-expo
Circ $in-out-circ $in-circ $out-circ
Back $in-out-back $in-back $out-back

Reversed easings curves

For each of these variables, a reversed curve is available by adding the -r suffix to the variable name (or its alias). Examples:

  • $ease-in-out-quart-r is the reversed curve of $ease-in-out-quart;
  • $out-expo-r is the reversed curve of $out-expo.


Write your timing functions powered by CSS Custom Properties the way you want:

.my-class {

  // using a custom property…
  transition: opacity 1.3s var(--in-out-circ);

  // … or a SCSS variable (Bourbon naming)
  transition: opacity 1.3s $ease-in-out-circ;

  // … or a shorter SCSS variable
  transition: opacity 1.3s $in-out-circ;

These syntaxes all lead to the same CSS output:

.my-class {
  transition: opacity 1.3s var(--in-out-circ);

💡 If you use Bourbon, no code change is required. Make sure you @import easings.scss after Bourbon, and you’re all set.

Custom easings

easings.scss also adds a bezier() function that alias the CSS cubic-bezier() one, allowing a shorter syntax for your custom easings.

// You can now write this…
.my-class {
  transition-timing-function: bezier(.1, .02, 1, .7);

// … instead of
.my-class {
  transition-timing-function: cubic-bezier(.1, .02, 1, .7);

Reverse easings

If you want to reverse a custom easing curve, you can use the reverse-bezier() function (or its alias r-bezier()), accepting 1 or 4 parameters.

// 4 parameters

.my-class {
  transition-timing-function: reverse-bezier(.1, .02, 1, .7);

// 1 parameter

$my-curve-not-reversed-yet: .1, .02, 1, .7;

.my-class {
  transition-timing-function: reverse-bezier($my-curve-not-reversed-yet);

// r-bezier alias

.my-class {
  transition-timing-function: r-bezier(.1, .02, 1, .7);


💡 easings.scss supports both the old and the new (2020) SASS specification, but aside from the installation step, the usage of the library remains the same in both spec.

If you’re not sure which one your project uses, this might help.
  • If the project uses node-sass or if you import SCSS files using @import, there’s a high chance you are using the old spec.
  • If the project uses Dart SASS (sass) and if you import SCSS files using @use or @forward, you are using the new spec.
  • In the new spec, @import is deprecated and variables are not global. This is why easings.scss usage isn’t the same changes depending on the spec.

Projects using Dart SASS

Dart SASS support starts at version 1.0.

  • npm install easings.scss pulls the package into your project;
  • @use 'easings.scss' as *; in a SCSS file make all the easings available as SCSS variables in addition to adding them at :root level.

Projects using node-sass

  1. npm install easings.scss@node-sass pulls the package into your project.
  2. @import '~easings.scss'; in a SCSS file make all the easings available as SCSS variables in addition to adding them at :root level.

Full import

The sole @import or @use statement…

@use 'easings.scss'; // easings.scss 1.x
@import 'easings.scss'; // easings.scss 0.x

… already outputs:

:root {
  --in-sine: cubic-bezier(0.47, 0, 0.745, 0.715);
  --out-sine: cubic-bezier(0.39, 0.575, 0.565, 1);
  --in-out-sine: cubic-bezier(0.445, 0.05, 0.55, 0.95);
  --in-quad: cubic-bezier(0.55, 0.085, 0.68, 0.53);
  /* all 18 other easings… */
  --out-back: cubic-bezier(0.175, 0.885, 0.32, 1.275);
  --in-out-back: cubic-bezier(0.68, -0.55, 0.265, 1.55);


Partial import ($easings)

If you don’t want to import everything, write an $easings list before the @use (or @import) statement:

// your minimal list of easings
$easings: 'in-out-quad', 'in-out-quad-r', 'out-circ', 'in-out-back';

@use 'easings.scss' with($easings: $easings); // easings.scss 1.x
@import 'easings.scss'; // easings.scss 0.x

This will only output the needed Custom Properties, instead of the 24 available:

:root {
  --in-out-quad: cubic-bezier(0.455, 0.03, 0.515, 0.955);
  --in-out-quad-r: cubic-bezier(0.485, 0.045, 0.545, 0.97);
  --out-circ: cubic-bezier(0.075, 0.82, 0.165, 1);
  --in-out-back: cubic-bezier(0.68, -0.55, 0.265, 1.55);

💡Partial import is only impacting the generated custom properties, but all the 48 SCSS variables (and their aliases) remain available. In addition, the 48 cubic-bezier coordinates are also available with the -value suffix:

$in-out-cubic-value: 0.645, 0.045, 0.355, 1;
$in-out-cubic-r-value: 0.645, 0, 0.355, 0.955;

Legacy browsers ($easings-legacy)

If you don’t want to output custom properties, set $easings-legacy to true:

// easings.scss 1.x
@use 'easings.scss' with($easings-legacy: true);

// easings.scss 0.x
$easings-legacy: true;
@import 'easings.scss';

With this legacy flag, no CSS will be generated in :root. SCSS variables will output a cubic-bezier function instead of a Custom Property:

Example SCSS code:

.my-class {
  transition: opacity 1.3s $ease-in-out-circ;

Generated CSS:

/* with `$easings-legacy: true;` */
.my-class {
  transition: opacity 1.3s cubic-bezier(0.785, 0.135, 0.15, 0.86);

/* without `$easings-legacy` */
.my-class {
  transition: opacity 1.3s var(--in-out-circ);