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 could actually sluggish pages.
Splitt used a real-world instance on builders.google.com for example a typical 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 pictures to lazy loading, which isn’t nice.”
Splitt used the instance to clarify why lazy-loading hero pictures is dangerous: you inform the browser to attend on essentially the most seen component, which may push again LCP and trigger structure shifts if dimensions aren’t set.
Splitt stated:
“In case you are 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 could actually 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 property have already queued.
That delay shifts the paint time of the biggest component later, which will increase your LCP.
On sluggish networks or CPU-limited gadgets, the impact is extra noticeable. If width and peak are lacking, the late picture also can nudge structure and really feel “jarring.”
website positioning Threat With Some Libraries
Browsers now assist a built-in loading attribute for pictures 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 acquired a local attribute for pictures 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, pictures could 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 slightly 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 Verify Your Pages
Use Search Console’s URL Inspection to evaluation the rendered HTML and make sure that above-the-fold pictures 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 may be high quality.”
Rating Affect
Splitt framed rating results as modest. Core Internet Vitals contribute to rating, however he known as it “a tiny minute issue most often.”
What You Ought to Do Subsequent
- Preserve hero and different above-the-fold pictures keen with width and peak set.
- Use native loading=”lazy” for below-the-fold pictures and iframes.
- In the event you depend on a library for previews, movies, or dynamic sections, be sure the ultimate markup exposes actual URLs in customary 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 tendencies over time.
Featured Picture: Screenshot from YouTube.com/GoogleSearchCentral, August 2025.
