Learn how lazy loading can boost your website’s performance by deferring offscreen images and assets until users need them.
Web performance is a critical factor in user experience and SEO rankings. One effective technique to speed up your site is lazy loading, a strategy that delays the loading of non-critical resources—like images, videos, or iframes—until they’re about to enter the user’s viewport. Let’s explore why it matters and how to implement it.
Why Lazy Loading Matters
Users expect websites to load fast. According to studies, a one-second delay in page load time can drop conversion rates by 7%. Lazy loading reduces initial page weight, cutting down load times and bandwidth usage, especially on media-heavy sites. It’s a win for mobile users and a boost for your performance metrics like Largest Contentful Paint (LCP).
How to Implement Lazy Loading
Modern browsers make lazy loading a breeze with the loading="lazy" attribute for images and iframes. Here’s a quick example:
This tells the browser to load the image only when it’s near the viewport. For older browsers, you can use JavaScript libraries like Lozad.js or Intersection Observer API for more control:
Pair this with <img data-src="example-image.jpg" alt="Example"> in your HTML.
Best Practices
- Prioritize above-the-fold content: Don’t lazy-load hero images or critical assets users see first.
- Test across devices: Ensure lazy loading doesn’t break layouts or user experience.
- Use placeholders: Low-res images or solid colors can smooth the transition as assets load.
Bonus Tip
If you’re building with a CMS like Sanity (wink), lazy loading pairs beautifully with dynamic content. Fetch image metadata via Sanity’s CDN and apply loading="lazy" programmatically in your front-end template.
