In a current episode of Google’s Search Off the Document podcast, Martin Splitt and John Mueller mentioned when lazy loading helps and when it may possibly gradual pages.
Splitt used a real-world instance on builders.google.com for instance a typical sample: making each picture lazy by default can delay Largest Contentful Paint (LCP) if it contains above-the-fold visuals.
Splitt mentioned:
“The content material administration system that we’re utilizing for builders.google.com … defaults all photographs to lazy loading, which isn’t nice.”
Splitt used the instance to elucidate why lazy-loading hero photographs is dangerous: you inform the browser to attend on probably the most seen component, which may push again LCP and trigger format shifts if dimensions aren’t set.
Splitt mentioned:
“If you’re utilizing lazy loading on a picture that’s instantly seen, that’s most certainly going to have an effect in your largest contentful paint. It’s like virtually assured.”
How Lazy Loading Delays LCP
LCP measures the second the biggest textual content or picture within the preliminary viewport is painted.
Usually, the browser’s preload scanner finds that hero picture early and fetches it with excessive precedence so it may possibly paint quick.
While you add loading="lazy" to that very same hero, you alter the browser’s scheduling:
- The picture is handled as decrease precedence, so different assets begin first.
- The browser waits till format and different work progress earlier than it requests the hero picture.
- The hero then competes for bandwidth after scripts, types, and different belongings have already queued.
That delay shifts the paint time of the biggest component later, which will increase your LCP.
On gradual networks or CPU-limited units, the impact is extra noticeable. If width and top are lacking, the late picture may nudge format and really feel “jarring.”
web optimization Threat With Some Libraries
Browsers now help a built-in loading attribute for photographs and iframes, which removes the necessity for heavy JavaScript in commonplace eventualities. WordPress adopted native lazy loading by default, serving to it unfold.
Splitt mentioned:
“Browsers obtained a local attribute for photographs and iframes, the loading attribute … which makes the browser maintain the lazy loading for you.”
Older or customized lazy-loading libraries can conceal picture URLs in nonstandard attributes. If the actual URL by no means lands in src or srcset within the HTML Google renders, photographs could not get picked up for indexing.
Splitt mentioned:
“We’ve seen a number of lazy loading libraries … that use some type of data-source attribute somewhat than the supply attribute… If it’s not within the supply attribute, we gained’t decide it up if it’s in some customized attribute.”
How To Examine Your Pages
Use Search Console’s URL Inspection to evaluate the rendered HTML and make sure that above-the-fold photographs and lazy-loaded modules resolve to plain attributes. Keep away from counting on the screenshot.
Splitt suggested:
“If the rendered HTML seems prefer it incorporates all of the picture URLs within the supply attribute of a picture tag … then you may be superb.”
Rating Influence
Splitt framed rating results as modest. Core Net Vitals contribute to rating, however he known as it “a tiny minute issue typically.”
What You Ought to Do Subsequent
- Hold hero and different above-the-fold photographs keen with width and top set.
- Use native
loading="lazy"for below-the-fold photographs and iframes. - For those who depend on a library for previews, movies, or dynamic sections, ensure that the ultimate markup exposes actual URLs in commonplace attributes, and make sure in rendered HTML.
Wanting Forward
Lazy loading is beneficial when utilized selectively. Deal with it as an opt-in for noncritical content material.
Confirm your implementation with rendered HTML, and watch how your LCP traits over time.
Featured Picture: Screenshot from YouTube.com/GoogleSearchCentral, August 2025.Â