Web animations can make a website feel dynamic and engaging. However, when animations cause layout shifts, it can create a jarring user experience, where elements unexpectedly jump around on the screen. This can frustrate users and hurt your website’s performance metrics, like Cumulative Layout Shift (CLS), which directly impacts SEO rankings.
In this guide, you’ll learn what layout shifts are, why they happen during animations, and how to avoid them. By following these best practices, you can ensure that your web animations remain smooth and stable, providing a better experience for users and improving your site’s performance on Google.
What Is Layout Shift?A layout shift happens when visible elements on a webpage change position or size unexpectedly, causing other elements to move. This is especially problematic when users are interacting with your site, leading to accidental clicks and a poor user experience.
Google’s Cumulative Layout Shift (CLS) measures how much a page’s content moves during the page’s lifecycle. A high CLS score negatively impacts both user satisfaction and SEO rankings.
Example of Layout ShiftConsider a button you’re about to click. If an image above it loads late and pushes the button down, the layout shifts, and you may accidentally click the wrong button.
Why Do Layout Shifts Happen During Animations?Layout shifts during animations typically occur because the browser needs to reflow and repaint the page when certain CSS properties change. Animating properties like width, height, margin, or top/left can trigger these reflows, causing other elements to move.
Best Practices to Avoid Layout Shifts in Web Animations1. Animate Transform and Opacity, Not Layout Properties
When animating elements, stick to properties that don’t affect the overall layout of the page. transform and opacity are the best options since they don’t trigger layout recalculations, meaning they don’t cause shifts.
Example
/* Smooth hover effect using transform and opacity */
.card {
transition: transform 0.3s ease, opacity 0.3s ease;
}
.card:hover {
transform: scale(1.05) translateY(-10px);
opacity: 0.9;
}
In the above example, the hover effect smoothly moves and scales the card without triggering a layout shift.
2. Reserve Space for Dynamic Content
One of the main causes of layout shifts is dynamically loaded content, such as images, ads, or third-party scripts. To avoid this, reserve space in advance by defining width and height attributes for images or containers.
<img src="image.jpg" alt="example" width="600" height="400" />
By specifying the size of the image upfront, the browser knows exactly how much space to allocate, preventing layout shifts when the image loads.
3. Use CSS contain Property
The CSS contain property allows you to limit the scope of an element’s influence on the rest of the page. This can prevent layout shifts by isolating animations within a certain area.
/* Contain layout changes within this container */
.animated-container {
contain: layout;
}
This prevents animations inside the .animated-container from affecting other elements outside the container.
4. Avoid Animating Top/Left/Right/Bottom Properties
Animating layout-affecting properties like top, left, right, or bottom causes a reflow and may lead to layout shifts. Instead, use transform to move elements without affecting the surrounding layout.
/* Bad: causes layout shift */
.bad-example {
transition: top 0.3s ease;
position: relative;
}
.bad-example:hover {
top: 20px;
}
/* Good: smooth movement without layout shift */
.good-example {
transition: transform 0.3s ease;
}
.good-example:hover {
transform: translateY(20px);
}
5. Use Font Loading Strategies
Fonts can cause layout shifts if they load late or if the fallback font has different metrics. Use font-display: swap; to ensure a fallback font is used while the custom font loads, preventing a shift in text layout.
@font-face {
font-family: 'CustomFont';
src: url('customfont.woff2') format('woff2');
font-display: swap;
}
This ensures text remains visible during font loading and prevents reflow when the custom font is applied.
6. Monitor and Optimize CLS with Tools
To ensure your animations aren’t contributing to layout shifts, use tools like Google Lighthouse or Chrome’s Web Vitals Extension to monitor your CLS score.
- Lighthouse: Generate a performance report that highlights layout shift issues.
- Web Vitals Extension: Track real-time CLS, Largest Contentful Paint (LCP), and First Input Delay (FID).
Run a Lighthouse audit by opening DevTools in Chrome (Right-click -> Inspect -> Lighthouse) and see your site’s CLS score along with suggestions for improvement.
Bonus Tip: Smooth Animations for User Delight
While it’s important to avoid layout shifts, animations themselves can enhance user experience when used correctly. Consider adding micro-interactions like hover effects, button feedback, or subtle animations to guide users and make your site feel polished and responsive—just be sure they don’t cause layout shifts!
Conclusion
Avoiding layout shifts in web animations not only improves user experience but also boosts your SEO rankings. By sticking to properties like transform and opacity, reserving space for dynamic content, and monitoring your CLS score, you can create animations that are smooth, stable, and SEO-friendly.
Take the time to optimize your web animations today, and enjoy faster, more user-friendly websites that both users and Google will love!
Key Takeaways:- Avoid animating properties that affect the layout, such as width, height, and top/left.
- Reserve space for images and dynamic content to prevent layout shifts.
- Use tools like Lighthouse to measure and optimize your CLS score.
By following these guidelines, your site will provide a smooth, seamless experience and rank better on Google, all while delighting users with polished animations.