In a current episode of Google’s Search Off the File podcast, Martin Splitt and John Mueller mentioned when lazy loading helps and when it might gradual pages.
Splitt used a real-world instance on builders.google.com as an example a standard sample: making each picture lazy by default can delay Largest Contentful Paint (LCP) if it consists of above-the-fold visuals.
Splitt stated:
“The content material administration system that we’re utilizing for builders.google.com … defaults all photos to lazy loading, which isn’t nice.”
Splitt used the instance to clarify why lazy-loading hero photos is dangerous: you inform the browser to attend on probably the most seen ingredient, which may push again LCP and trigger structure shifts if dimensions aren’t set.
Splitt stated:
“If you’re utilizing lazy loading on a picture that’s instantly seen, that’s probably 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 might paint quick.
Once you add loading="lazy" to that very same hero, you alter the browser’s scheduling:
- The picture is handled as decrease precedence, so different sources begin first.
- The browser waits till structure 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 ingredient later, which will increase your LCP.
On gradual networks or CPU-limited units, the impact is extra noticeable. If width and peak are lacking, the late picture can even nudge structure and really feel “jarring.”
website positioning Danger With Some Libraries
Browsers now help a built-in loading attribute for photos and iframes, which removes the necessity for heavy JavaScript in customary situations. WordPress adopted native lazy loading by default, serving to it unfold.
Splitt stated:
“Browsers bought a local attribute for photos and iframes, the loading attribute … which makes the browser handle the lazy loading for you.”
Older or customized lazy-loading libraries can disguise picture URLs in nonstandard attributes. If the true URL by no means lands in src or srcset within the HTML Google renders, photos might not get picked up for indexing.
Splitt stated:
“We’ve seen a number of lazy loading libraries … that use some type of data-source attribute moderately 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 Test Your Pages
Use Search Console’s URL Inspection to evaluation the rendered HTML and make sure that above-the-fold photos and lazy-loaded modules resolve to straightforward attributes. Keep away from counting on the screenshot.
Splitt suggested:
“If the rendered HTML seems prefer it comprises all of the picture URLs within the supply attribute of a picture tag … then you can be high quality.”
Rating Affect
Splitt framed rating results as modest. Core Net Vitals contribute to rating, however he known as it “a tiny minute issue usually.”
What You Ought to Do Subsequent
- Hold hero and different above-the-fold photos keen with width and peak set.
- Use native
loading="lazy"for below-the-fold photos and iframes. - When you depend on a library for previews, movies, or dynamic sections, be certain the ultimate markup exposes actual URLs in customary attributes, and make sure in rendered HTML.
Trying 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.
