Crafting Smooth Cross-Browser Scrolling Experiences

Scrolling serves as the heartbeat of UI interactions across the web. Getting smooth scroll performance right is essential for happy users and healthy metrics.

Thankfully, modern browsers provide powerful capabilities for customizing scroll experiences. Combined with robust testing tools, we can build flows feeling magical across environments.

In this deep dive, you’ll learn:

• The business impact of smoothing scroll jank
• CSS and JavaScript techniques for buttery smoothness
• Optimizations for lag-free 60fps interactions
• Considerations around accessibility and inclusivity
• Battle-tested approaches for tackling cross-browser quirks

Let’s get scrolling!

Why Smooth Scrolling Matters

Before diving into code, let‘s discuss why tackling scroll performance is so crucial.

Scrolling Dominates Actions on Web

According to web tracking data:

• Up to 80% of all user actions on mobile web involve scrolling
• The average mobile session contains over 150 scroll events

With scrolling so prevalent, optimization opportunities abound!

Scroll Jank Harms Engagement

Studies by Google show:

• 47% of mobile site visitors will leave a lagging page
• 2x higher bounce rates when scroll chugs below 60fps

Prioritizing smoothness pays off handsomely.

SmoothnessSignals Quality

Smoothing harsh scroll behaviors:

• Increases average session times by 32%
• Converts more sales through seamless microinteractions

Set your product apart with buttery smoothness!

Browser Compatible CSS Smooth Scrolling

The simplest way to add smooth scrolling relies solely on CSS.

Leveraging Scroll Behavior

Modern browsers support customizing scroll behavior via:

scroll-behavior: smooth;

This curves scrolling based on easing preferences to smooth transitions between viewport destinations.

For example:

html {
  scroll-behavior: smooth;
}

a[href*="#"] {
  scroll-behavior: smooth; 
} 

The first rule smooths all page scrolling. The second smoothes anchor links clicks.

Demo Snippet

Here‘s a demo applying smooth scroll behavior on anchor links:

<!-- HTML -->
<nav>
  <a href="#section-1">Section 1</a>
  <a href="#section-2">Section 2</a>
</nav>

<div id="section-1">I‘m Section 1!</div>  
<div id="section-2">I‘m Section 2!</div>

<!-- CSS -->
a[href*="#"] {
  scroll-behavior: smooth; 
}

This slides content into view on link click rather than harsh jumping!

[[Embed demo snippet]]

Customizing Easing

We can pass easing preferences into scroll-behavior like:

scroll-behavior: smooth cubic-bezier(.64,.04,.35,.67);

This eases based on custom bezier curve for unique feel!

Browser Compatibility Fallbacks

The scroll-behavior property offers 98% browser support – but lacks in older browsers versions still in significant use.

We address this through progressive enhancement:

html {
  scroll-behavior: smooth;
}

html.no-smoothscroll {
  scroll-behavior: auto; 
}

The second rule overrides smoothing when unsupported. We toggle the .no-smoothscroll class accordingly in JavaScript.

This saves anyone from missing out!

Enabling Smooth Scrolling in JavaScript

For greater control beyond CSS, we can animate scroll positions in JavaScript.

Popular scrolling methods include:

scrollTo – Scrolls page to specific pixel offset

scrollBy – Scrolls relative to current position

scrollIntoView – Scrolls element into viewport

For example:

document.querySelector("#section-2").scrollIntoView({ 
  behavior: "smooth"
});

This smoothly scrolls #section-2 into visible area on command!

We abstract smooth behaviors into reusable functions:

function smoothScrollTo(position) {
  window.scrollTo({
    left: 0,
    top: position, 
    behavior: "smooth"
  });
}

let section2Position = document.querySelector("#section-2").offsetTop;

smoothScrollTo(section2Position); 

Encapsulating scroll logic keeps things DRY endure maintainable.

Customizing Easing Curves

Beyond browser defaults, we can fully customize scroll easing physics with requestAnimationFrame():

function smoothScrollTo(position) {

  let start = window.scrollY;
  let distance = position - start;
  let startTime = null;

  function animation(currentTime) {
    if (!startTime) {  
      startTime = currentTime;
    }

    let timeElapsed = currentTime - startTime;
    let percentage = Math.min(timeElapsed / 1000, 1); 

    window.scrollTo(0, distance * easing(percentage) + start)

    if (percentage < 1) {
      requestAnimationFrame(animation)
    }
  }

  requestAnimationFrame(animation)

}

let easing = (t) => t < 0.5 ? 4 * t * t * t : (t - 1) * (2 * t - 2) * (2 * t - 2) + 1; // Accelerate then deccelerate

This drives scroll through buttery smooth easing physics!

Leveraging Scroll Libraries

For convenience, we can leverage pre-packaged smooth scroll libraries like SmoothScroll.

import SmoothScroll from ‘smooth-scroll‘;

let scroll = new SmoothScroll(‘a[href*="#"]‘); 

These abstract vendor differences and handle edge cases behind consistent APIs.

Want parallax scrolling? Check outfull-featured options like ScrollMagic and Locomotive!

Optimizing Scroll Performance

Achieving consistent 60 FPS during scroll handling is key for maximum smoothness.

Using will-change

The will-change property hints impending visual changes so the browser can optimize handling ahead of time.

For example:

.smooth-page {
  will-change: transform;
}

This prompts the creation of a GPU layer for buttery composition.

Avoiding Layout Thrashing

Layout thrashing happens when style changes trigger expensive recalculation cycles:

We avoid this by isolating paints from handler logic:

.smooth-container {
  will-change: transform;
  transform: translateZ(0); 
}

translateZ shifts visual updates to the composite thread off the main thread.

Check out Graphics Performance in Chrome DevTools to confirm optimizations!

Building Accessible Smooth Scrolling

When enhancing scroll, ensure we don‘t reduce accessibility in the process!

Supporting User Preferences

Some users suffer motion sickness or vertigo from accelerated scrolling. We respect user choice through the prefers-reduced-motion media query:

@media (prefers-reduced-motion) {
  html {
    scroll-behavior: auto;  
  }
}

This disables smooth scrolling for those requiring more static interactions.

Provide toggles to override animated behaviors:

<button id="reduceMotionButton">Reduce Motion</button>

<script>
const reduceMotionButton = document.getElementById(‘reduceMotionButton‘);

reduceMotionButton.addEventListener(‘click‘, () => {
  document.body.classList.add(‘reduced-motion‘);  
})  
</script>

<style>
.reduced-motion html {
  scroll-behavior: auto;
} 
</style>

Empower users take control when needed!

Supporting Keyboard Users

Smooth, visually-oriented scroll animations can disorient users of keyboard/assistive technologies.

Ensure keyboarding behaves predictably for full accessibility:

• Page Up/Down keys match visual scroll increments
• Focus visibly tracks position shifts during smooth scroll animations
• Landmarks provide orientation when skipping sections

Review WebAIM for comprehensive best practices.

Rigorously Testing Cross-Browser Compatibility

With diverse browsing environments, consistently test across:

• Desktop vs mobile devices
• Major web browsers like Chrome, Firefox and Safari
• Modern vs legacy browser versions
• High vs low performance device profiles

Manually testing device/browser matrices scales poorly. Instead, leverage services like BrowserStack Live to confirm consistent UX in target environments before release.

BrowserStack provides instant access to 3000+ real mobile devices and browsers running in the cloud. We validate smooth scrolling implementations to catch issues under real user conditions!

Debugging Scroll Performance

When things go wrong, Chrome DevTools provides robust profiling to trace culprits harming smoothness.

The Performance Panel

Capture traces during scroll handling to inspect:

• Main thread workload breakdown
• Framerate over time
• Style/layout inefficiencies

The Layers Panel

Inspect layer construction and GPU consumption during interactions.

Scroll Timeline

The Scroll timeline visualizes frame by frame rendering clearly surfaces janky stretches harming fluidity.

For smooth profiling across environments, BrowserStack Insights for Web aggregates performance metrics across real devices:

Targeted optimizations is a numbers game backed by data!

Scrolling Confidently Ahead

There you have it – everything you need for achieving flawless smooth scrolling implementations.

To recap:

• Use CSS scroll-behavior for smoothing declaratively
• Animate scroll positions in JavaScript for control
• Stress test on diverse real devices pre-release
• Optimize continuos 60fps rendering
• Support inclusive access through preferences

With powerful modern web capabilities, crafting magical flowing experiences is more achievable than ever.

Now get scrolling smoothly ahead!

Let me know if you have any other questions!