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ScrollSmoother.create( ) ;


Creates (and returns) a new ScrollSmoother instance. There can only be one, of course, at any given time because it's controlling the scroll of the root page. If a ScrollSmoother instance already exists, its kill() method will be called before creating the new one in the ScrollSmoother.create() call. If you want to get a reference to the ScrollSmoother that was already created, use the ScrollSmoother.get() method.


Your HTML content should reside in a single content element (usually a<div>but it doesn't really matter) - that's what gets moved around when the user scrolls. That content element is wrapped in a wrapper element that serves as the viewport. The actual scrollbar remains on the <body>, so your setup would look like:

<div id="smooth-wrapper">
<div id="smooth-content">

Under the hood, everything flows through ScrollTrigger which watches the page's native scroll position and then ScrollSmoother applies transforms to the content to gradually catch up with that scroll position. So if you suddenly drag the native scrollbar 500px, ScrollSmoother will gradually move the content to that spot using inline CSS transforms (matrix3d()) on the content. Since ScrollSmoother is built on top of ScrollTrigger, don't forget to register them both:

gsap.registerPlugin(ScrollTrigger, ScrollSmoother);

Usage & special properties

The configuration object can have any of the following optional properties:

Speed (parallax)

When you set effects: true, ScrollSmoother finds all elements that have a data-speed attribute and applies a parallax effect accordingly so that they move at the designated speed. For example:

<div data-speed="0.5"></div> <!-- half-speed of scroll -->
<div data-speed="2"></div> <!-- double-speed of scroll -->
<div data-speed="1"></div> <!-- normal speed of scroll -->
<div data-speed="auto"></div> <!-- auto-calculated based on how far it can move inside its container -->

"auto" speed

When you set the speed to "auto", it will calculate how far it can move inside its parent container in the direction of the largest gap (up or down). So it's perfect for parallax effects - just make the child larger than its parent, align it where you want it (typically its top edge at the top of the container, or the bottom edge at the bottom of the container) and let ScrollSmoother do its magic. Obviously set overflow: hidden on the parent so it clips the child.

clamp() speed effects

Have you ever had an element that you natively placed toward the very top of your page but when you apply a data-speed, it starts out shifted from its native position? That's because by default, speed effects cause elements to reach their "native" position when centered vertically in the viewport, so they'll likely start out offset. Starting in version 3.12, you can wrap your speed value in "clamp()" to make them start out in their native position if they're "above the fold" (inside the viewport when scrolled to the very top). Under the hood, data-speed effects are driven by ScrollTrigger instances, so this a way to employ ScrollTrigger's clamp() feature that prevents the start/end values from "leaking" outside the page bounds (never less than 0 and never more than the maximum scroll position). For example:

<div data-speed="clamp(0.5)"></div> <!-- clamped half-speed -->

You can also use the effects() method to dynamically apply speed or lag effects to targets (including function-based ones). Note: effects should not be nested.

let scroller = ScrollSmoother.create({...});
scroller.effects(".box", {speed: 0.5, lag: 0.1});

Keep in mind that the elements will hit their "natural" position in the CENTER of the viewport. Here's a visual demo from @snorkltv:


Lag (the delightful kind)

Think of a "lag" like making the element lazy, allowing it to drift from its normal scroll position, taking a certain amount of time to "catch up". You can assign slightly different lags to elements in close proximity to give them a staggered effect when scrolling that's quite pleasing to the eye. If you set effects: true on the ScrollSmoother.create() config, it'll automatically find any elements with the data-lag attribute and apply that effect:

<div data-lag="0.5"></div> <!-- takes 0.5 seconds to "catch up" -->
<div data-lag="0.8"></div> <!-- takes 0.8 seconds to "catch up" -->

You can also use the effects() method to dynamically apply speed or lag effects to targets (including function-based ones) via JavaScript.

let scroller = ScrollSmoother.create({...});
scroller.effects(".box", {lag: 0.5, speed: 1});