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Animate on scroll library

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AOS - Animate on scroll library

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:exclamation::exclamation::exclamation: This is README for [email protected] :exclamation::exclamation::exclamation:

For last stable release (v2) go here

🚀 Demo

🌟 Codepen Examples

👉 To get a better understanding how this actually works, I encourage you to check my post on CSS-tricks.

⚙ Installation


Add styles in


Add script right before closing

 tag, and initialize AOS:

Using package managers


package: *
yarn add [email protected]
* or
npm install --save [email protected]

Import script, styles and initialize AOS:

import AOS from 'aos';
import 'aos/dist/aos.css'; // You can also use  for styles
// ..

In order to make it work you'll have to make sure your build process has configured styles loader, and bundles it all correctly. If you're using Parcel however, it will work out of the box as provided.

🤔 How to use it?

1. Initialize AOS:


// You can also pass an optional settings object // below listed default settings AOS.init({ // Global settings: disable: false, // accepts following values: 'phone', 'tablet', 'mobile', boolean, expression or function startEvent: 'DOMContentLoaded', // name of the event dispatched on the document, that AOS should initialize on initClassName: 'aos-init', // class applied after initialization animatedClassName: 'aos-animate', // class applied on animation useClassNames: false, // if true, will add content of data-aos as classes on scroll disableMutationObserver: false, // disables automatic mutations' detections (advanced) debounceDelay: 50, // the delay on debounce used while resizing window (advanced) throttleDelay: 99, // the delay on throttle used while scrolling the page (advanced)

// Settings that can be overridden on per-element basis, by data-aos-* attributes: offset: 120, // offset (in px) from the original trigger point delay: 0, // values from 0 to 3000, with step 50ms duration: 400, // values from 0 to 3000, with step 50ms easing: 'ease', // default easing for AOS animations once: false, // whether animation should happen only once - while scrolling down mirror: false, // whether elements should animate out while scrolling past them anchorPlacement: 'top-bottom', // defines which position of the element regarding to window should trigger the animation


2. Set animation using


And adjust behaviour by using

attributes: ```html <div data-aos="fade-up" data-aos-offset="200" data-aos-delay="50" data-aos-duration="1000" data-aos-easing="ease-in-out" data-aos-mirror="true" data-aos-once="false" data-aos-anchor-placement="top-center"


See full list of all animations, easings and anchor placements


There is also a setting that can be used only on per-element basis: *

- element whose offset will be used to trigger animation instead of an actual one.



This way you can trigger animation on one element, while you scroll to another - useful in animating fixed elements.


AOS object is exposed as a global variable, for now there are three methods available:

  • init
    - initialize AOS
  • refresh
    - recalculate all offsets and positions of elements (called on window resize)
  • refreshHard
    - reinit array with AOS elements and trigger
    (called on DOM changes that are related to

Example execution:


By default AOS is watching for DOM changes and if there are any new elements loaded asynchronously or when something is removed from DOM it calls

automatically. In browsers that don't support
like IE you might need to call
by yourself.

method is called on window resize and so on, as it doesn't require to build new store with AOS elements and should be as light as possible.

JS Events

AOS dispatches two events on document:

whenever any element animates in or out, so that you can do extra stuff in JS: ```js document.addEventListener('aos:in', ({ detail }) => { console.log('animated in', detail); });

document.addEventListener('aos:out', ({ detail }) => { console.log('animated out', detail); }); ```

You can also tell AOS to trigger custom event on specific element, by setting


Then you'll be able to listen for two custom events then: -



Adding custom animations:

Sometimes built-in animations are just not enough. Let's say you need one box to have different animation depending on resolution. Here's how you could do it:

[data-aos="new-animation"] {
  opacity: 0;
  transition-property: transform, opacity;

&.aos-animate { opacity: 1; }

@media screen and (min-width: 768px) { transform: translateX(100px);

&amp;.aos-animate {
  transform: translateX(0);

} }

Then use it in HTML:

The element will only animate opacity on mobile devices, but from 768px width it'll also slide from right to left.

Adding custom easing:

Similar to animations you can add custom easings:

[data-aos] {
  body[data-aos-easing="new-easing"] &,
  &[data-aos][data-aos-easing="new-easing"] {
    transition-timing-function: cubic-bezier(.250, .250, .750, .750);

Customizing default animations distance

Default distance for built-in animations is 100px. As long as you're using SCSS though, you can override it:

$aos-distance: 200px; // It has to be above import
@import 'node_modules/aos/src/sass/aos.scss';
You have to however configure your build process to allow it to import styles from

Integrating external CSS animation library (e.g. Animate.css):


to change default behaviour of AOS, to apply class names placed inside
on scroll.
  useClassNames: true,
  initClassName: false,
  animatedClassName: 'animated',

The above element will get two classes:

. Using different combinations of the three above settings, you should be able to integrate any external CSS animation library.

External libraries however don't care too much about animation state before the actual animation. So if you want those elements to be not visible before scrolling, you might need to add similar styles:

[data-aos] {
  visibility: hidden;
[data-aos].animated {
  visibility: visible;



Duration and delay accept values from 50 to 3000, with step 50ms, it's because those are handled by css, and to not make css longer than it is already I implemented only a subset. I believe those should cover most cases.

If not, you can write simple CSS that will add another duration, for example:

  body[data-aos-duration='4000'] [data-aos],
  [data-aos][data-aos][data-aos-duration='4000'] {
    transition-duration: 4000ms;

This code will add 4000ms duration available for you to set on AOS elements, or to set as global duration while initializing AOS script. Notice that double

- it's not a mistake, it is a trick, to make individual settings more important than global, without need to write ugly "!important" there :)

Example usage:


Predefined options


  • Fade animations:

    • fade
    • fade-up
    • fade-down
    • fade-left
    • fade-right
    • fade-up-right
    • fade-up-left
    • fade-down-right
    • fade-down-left
  • Flip animations:

    • flip-up
    • flip-down
    • flip-left
    • flip-right
  • Slide animations:

    • slide-up
    • slide-down
    • slide-left
    • slide-right
  • Zoom animations:

    • zoom-in
    • zoom-in-up
    • zoom-in-down
    • zoom-in-left
    • zoom-in-right
    • zoom-out
    • zoom-out-up
    • zoom-out-down
    • zoom-out-left
    • zoom-out-right

Anchor placements:

  • top-bottom
  • top-center
  • top-top
  • center-bottom
  • center-center
  • center-top
  • bottom-bottom
  • bottom-center
  • bottom-top

Easing functions:

  • linear
  • ease
  • ease-in
  • ease-out
  • ease-in-out
  • ease-in-back
  • ease-out-back
  • ease-in-out-back
  • ease-in-sine
  • ease-out-sine
  • ease-in-out-sine
  • ease-in-quad
  • ease-out-quad
  • ease-in-out-quad
  • ease-in-cubic
  • ease-out-cubic
  • ease-in-out-cubic
  • ease-in-quart
  • ease-out-quart
  • ease-in-out-quart


If you found a bug, have a question or an idea, please check AOS contribution guide and don't hesitate to create new issues.

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