Welcome to a tutorial on how to add smooth scroll animation in CSS and Javascript. Is the “suddenly scroll to” too abrupt for you? Well, it is actually very easy to add smooth scroll animations with modern CSS these days.
The easiest way to add a smooth scroll animation is to set the scroll behavior property in CSS – body { scroll-behavior: smooth }
That covers the basics, but let us walk through some examples and Javascript fallback in this guide – Read on!
ⓘ I have included a zip file with all the source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.
TLDR – QUICK SLIDES
Fullscreen Mode – Click Here
TABLE OF CONTENTS
DOWNLOAD & NOTES
Firstly, here is the download link to the example code as promised.
QUICK NOTES
If you spot a bug, feel free to comment below. I try to answer short questions too, but it is one person versus the entire world… If you need answers urgently, please check out my list of websites to get help with programming.
EXAMPLE CODE DOWNLOAD
Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.
SMOOTH SCROLL
All right, let us now get into the various ways and examples of how to do a smooth scroll.
1) PURE CSS SMOOTH SCROLL
<!-- (A) CSS SMOOTH SCROLL -->
<style>
html { scroll-behavior: smooth; }
</style>
<!-- (B) SCROLL TO TOP -->
<p id="top">Top of page</p>
<div style="height: 1500px; width: 100%;"></div>
<a href="#top">Scroll to top</a>
Top of page
Yep, adding scroll-behavior: smooth
on the body
is actually all we need. The good news is that scroll-behavior
is already well-supported on most modern “A grade” browsers. But if you have to support ancient browsers, the below Javascript method 3 is the only way to go.
2) JAVASCRIPT SMOOTH SCROLL
2A) THE HTML
<!-- (A) SCROLL TO X,Y PIXELS FROM THE TOP -->
<button id="top" onclick="scrTo(0, 500)">
Scroll to 500 px from the top.
</button>
<!-- (B) SCROLL X,Y PIXELS FROM CURRENT POSITION -->
<div style="height: 1000px; width: 100%;"></div>
<button onclick="scrBy(0, 100)">
Scroll down 100 px from current.
</button>
<!-- (C) SCROLL TO HTML ELEMENT -->
<div style="height: 1000px; width: 100%;"></div>
<button onclick="scrInto('#top');">
Go to top.
</button>
2B) THE JAVASCRIPT
// (A) SCROLL TO EXACT POSITION
function scrTo(x, y) {
window.scroll({
left: x, top: y,
behavior: "smooth"
});
}
// (B) SCROLL FROM CURRENT POSITION
function scrBy(x, y) {
window.scrollBy({
left: x, top: y,
behavior: "smooth"
});
}
// (C) SCROLL TO HTML ELEMENT
function scrInto(id) {
document.querySelector(id).scrollIntoView({
behavior: "smooth"
});
}
For you guys who need to do some scrolling programmatically in Javascript, there are 3 essential functions – scroll()
, scrollBy()
, and scrollIntoView()
.
scroll()
will go to an exact specified position on the page (from the top, bottom, left, right).scrollBy()
will scroll with reference from the current position.scrollIntoView()
goes to a specified element.- Finally, we set the
behavior: "smooth"
option to indicate “use smooth scroll animation”.
P.S. As you can guess again, behavior: "smooth"
will not work in the older browsers. It will simply “immediately scroll to the specified spot”.
2C) THE DEMO
3) LEGACY JAVASCRIPT SMOOTH SCROLL
3A) THE HTML
<button id="top" onclick="sscroll('bottom');">
Go to bottom
</button>
<div style="height: 2000px; width: 100%;"></div>
<button id="bottom" onclick="sscroll('top');">
Go to top
</button>
3B) THE JAVASCRIPT
function sscroll (id) {
// (A) SCROLL PARAMETERS
var speed = 10, // Less = faster
step = 30, // Less = smoother but slower
click = 0;
// (B) GET CURRENT Y POSITION + TARGET Y POSITION
var fromY = self.pageYOffset ? self.pageYOffset : document.body.scrollTop ;
var target = document.getElementById(id);
var toY = target.offsetTop;
while (target.offsetParent && target.offsetParent != document.body) {
target = target.offsetParent;
toY += target.offsetTop;
}
// (C) SCROLL ANIMATION - DOWNWARDS
if (fromY < toY) {
for (var i=fromY; i<=toY; i+=step) {
if (i+step > toY) {
setTimeout("window.scrollTo(0, " + toY + ")", click * speed);
} else {
setTimeout("window.scrollTo(0, " + i + ")", click * speed);
}
click++;
}
}
// (D) SCROLL ANIMATION - UPWARDS
else {
for (var i=fromY; i>=toY; i-=step) {
if (i-step < toY) {
setTimeout("window.scrollTo(0, " + toY + ")", click * speed);
} else {
setTimeout("window.scrollTo(0, " + i + ")", click * speed);
}
click++;
}
}
}
Lastly, this is for you guys who have to support ancient browsers. This is the old-school way of smooth scrolling, and how it works is actually pretty simple:
- (B) Calculate the current and target Y-positions.
- (C & D) Then manually set a whole chain of
scrollTo()
on timerssetTimeout()
to slowly move towards the target.
EXTRA BITS & LINKS
That’s all for the main tutorial, and here is a small section on some extras and links that may be useful to you.
COMPATIBILITY CHECKS
- CSS Scroll Behavior – CanIUse
- Scroll Into View – CanIUse
CSS SMOOTH SCROLL
Property | Description | Reference Link |
scroll-behavior: smooth |
Do a smooth scroll, not an “instant scroll”. | MDN |
JAVASCRIPT SMOOTH SCROLL
Function | Description | Reference Link |
ELEMENT.scrollIntoView() |
Scroll this element into view. | MDN |
window.scroll() |
Scrolls to a given point on the page. | MDN |
window.scrollBy() |
Scrolls with reference to current position. | MDN |
For fallback, we use a series of scroll
with setTimeout
, so that it will create an illusion of slowly moving toward the target.
INFOGRAPHIC CHEAT SHEET

THE END
Thank you for reading, and we have come to the end of this guide. I hope that it has helped you with your project, and if you have anything to share with this guide, please feel free to comment below. Good luck and happy coding!