In this week’s #SPQuiz, we asked our followers on LinkedIn and X/Twitter whether adding the lazy loading attribute to images below the fold was a winning test for a local service provider. Our customer had large images below the fold showing examples of specific services offered at their locations, and they wanted to know if lazy loading would speed up page loading times enough to impact search performance.
Poll Results
One third of our customers though this test could be a winner, but two thirds believed it wasn't likely to impact rankings enough to detectably boost organic traffic. No one thought the test was likely to be negative.
The Case Study
Our customer wanted to explore the impact of implementing the loading="lazy" attribute on images located below the fold across a set of local service pages.
Lazy loading is a common performance optimization technique that defers the loading of non-critical images until they are needed. Images with this attribute don’t load until the user scrolls down far enough to see them on the page. This means that users who land on a page experience faster loading times for the content that they see immediately on entering that page.
Google’s ranking algorithms take page speed and performance into account, since better loading times tend to make users happier with their experience on a site. So, even though how an image loads has no direct impact on Google’s understanding of keywords, pages that load images efficiently can rank better just because they’re providing a better user experience. In extreme cases, improvements in page speed may even be enough to reduce bounce rates.
We hypothesized that by adding the lazy loading attribute to images below the fold, we would reduce the initial load time of these pages, thereby improving their Core Web Vitals scores and increasing the likelihood of higher rankings for relevant keywords.
What Was Changed
We added the loading="lazy" attribute to all image elements located below the fold on a group of local service landing pages. No other changes were made to content or page structure.
Results
The test returned inconclusive results. Since this result fell within our credible interval for no detectable impact, we cannot conclude that the lazy loading change had a meaningful impact on organic performance.
In this case, while our customer’s local service pages did have images below the fold that could load more efficiently, those images weren’t large and numerous enough to significantly change page loading times. As a result, deferring their load had little to no effect on the overall user experience or Core Web Vitals in a way that would impact search rankings. This suggests that lazy loading may not be a high-leverage change on these particular pages.
Adding the lazy loading attribute to below-the-fold images didn’t move the needle in this case, but that doesn’t mean performance optimizations aren’t valuable for search performance. By testing site improvements like this, you can measure the impact of changes instead of relying on assumptions or best practices, and you can make sure that your web development resources are going toward projects that will make a difference for your organic traffic.
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