Lazy Loading: Main Factor Affect Largest Contentful Paint (LCP)

Have you ever noticed a website where the main image takes too long to appear? That delay is often caused by lazy loading. But if you use it on above-the-fold images, it can slow down the Largest Contentful Paint (LCP). So how does lazy loading affect LCP and what can you do to fix it?

Google warns against lazy loading above-the-fold images

First, let’s find out what is lazy loading and largest contentful paint (LCP)?

Lazy loading is a technique used on websites to delay loading parts like images or videos until they are actually needed. It usually happens when a user scrolls to that part of the page. This helps the page load faster initially because the browser doesn’t load everything at once, saving time and data.

Largest Contentful Paint (LCP) is a web performance metric that measures how long it takes for the largest visible content (like a big image or a big block of text) on a webpage to fully appear on the screen. It shows how quickly users see important content when they visit a page. A fast LCP means a better user experience, and Google uses it to rank pages for search

So what’s happened?

Google is reminding site owners to be careful with lazy loading, especially for images that show up right away when a page opens. On a recent Search Off the Record podcast, Martin Splitt and John Mueller talked about how lazy loading can help but also hurt if used in the wrong place.

Splitt pointed out an example:

• From developers.google.com, where the system made every image lazy by default. That included the main hero image, which caused the Largest Contentful Paint (LCP) to slow down.

He explained that when you lazy-load an image that should appear instantly, you’re basically telling the browser to hold off on the most important element. This almost always delays LCP and can even cause layout shifts if the size isn’t set.

How lazy loading delays Largest Contentful Paint (LCP)?

Largest Contentful Paint (LCP) measures how quickly the biggest text or image in the first screen shows up. Normally, the browser spots the hero image right away and gives it high priority so it can load fast.

But when you add loading=”lazy” to that hero image, things change. The browser no longer sees it as urgent:

• It gives other files like scripts and styles a head start
• It waits until layout work is further along before asking for the image

By the time the request goes out, the image has to compete with everything else already in line

All of this pushes the hero image’s paint time further back, which slows down your LCP. On slower networks or weaker devices, the delay feels even worse. And if the image doesn’t have a width and height set, it can also shift the layout and make the page look uneven.

SEO risks with lazy-loading libraries

If lazy loading isn’t set up the right way, it can cause more harm than good. Some common issues include:

• Missed indexing: Older or custom libraries often hide image URLs inside made-up attributes like data-src instead of the real src or srcset. When that happens, Google may not see the images at all.
• Lost visibility in search: If Google can’t pick up your images, they won’t appear in Google Images or help with SEO value.
• Extra complexity:  Heavy JavaScript libraries add more code, slow down pages and aren’t needed now that browsers support the native loading attribute.
• Compatibility issues: Not all custom setups play nicely with modern browsers, making your web design Gold Coast harder to maintain and troubleshoot.

What should you do next?

To avoid Largest Contentful Paint (LCP) and SEO problems, you can follow a few simple steps:

• Don’t lazy load hero or above-the-fold images. Give them width and height.
• Use loading=”lazy” only for images and iframes lower on the page.
• If you use a library, make sure images have real URLs in src or srcset.
• Check in Search Console to see if Google can read your images.

Lazy loading is a great tool but only when used correctly. Keep your hero images eager, let the browser handle the rest and always double-check in Search Console. Small tweaks here can make a big difference to Largest Contentful Paint (LCP) and your visitors’ experience. Contact BRANDCOM, your trusted web design Gold Coast to bring the best experience to your customers!