Google's Core Web Vitals have been a ranking signal since 2021, but their impact extends far beyond SEO. For eCommerce businesses, these metrics directly correlate with revenue. Research from Google, Deloitte, and Vodafone consistently shows that faster, more stable web experiences drive measurably higher conversion rates. Here is what you need to know — and what you can do about it.
What Are Core Web Vitals?
Core Web Vitals are a set of three specific metrics that Google considers essential to a user's experience on a web page. They measure loading performance, interactivity, and visual stability. Together, they capture the most important aspects of how real users experience your site.
Largest Contentful Paint (LCP)
LCP measures how long it takes for the largest visible element on the page to render — typically a hero image, product photo, or large text block. Google considers a good LCP to be 2.5 seconds or less. For eCommerce, this metric is critical because it represents the moment a shopper can first see and evaluate your product or offer. Every 100 milliseconds of delay in LCP has been shown to correlate with a 1.11% decrease in session-based conversion rates, according to a Deloitte study for eBay.
Interaction to Next Paint (INP)
INP replaced First Input Delay (FID) in March 2024 as the responsiveness metric in Core Web Vitals. INP measures the latency of all interactions a user makes throughout their visit, and reports the worst interaction (with some outliers excluded). A good INP score is 200 milliseconds or less. For eCommerce, responsive interactions are essential for add-to-cart buttons, size selectors, filter controls, and search autocomplete — all of which directly influence purchasing decisions.
Cumulative Layout Shift (CLS)
CLS measures how much the page layout shifts unexpectedly during loading. A good CLS score is 0.1 or less. In eCommerce, layout shifts are particularly damaging — imagine a customer trying to tap "Add to Cart" when the button suddenly moves because an image or advertisement loaded above it. This frustration directly increases bounce rates and abandoned carts.
The Revenue Impact: What the Data Shows
The connection between Core Web Vitals and revenue is not theoretical. Multiple large-scale studies demonstrate a clear, causal relationship:
- Vodafone: A 31% improvement in LCP resulted in an 8% increase in sales and a 15% improvement in their lead-to-visit rate.
- NDTV: A 55% reduction in LCP led to a 50% decrease in bounce rate.
- Akamai: A 100-millisecond delay in load time can decrease conversion rates by up to 7%.
- Google research: Sites that meet all three Core Web Vitals thresholds see 24% fewer page abandonment rates.
How CWVs Affect Your Search Rankings
Core Web Vitals are a confirmed ranking signal in Google's algorithm. Whilst content relevance and backlinks remain more heavily weighted, page experience serves as a tiebreaker between otherwise equally relevant results. For competitive eCommerce keywords — where dozens of stores sell similar products — this tiebreaker can mean the difference between page one and page two.
Google Search Console provides a dedicated Core Web Vitals report that categorises your URLs as "Good," "Needs Improvement," or "Poor." Pages that fail CWV thresholds may be disadvantaged in mobile search results, where the majority of eCommerce browsing now occurs.
Optimisation Techniques for eCommerce
Improving LCP
- Optimise hero and product images: Use modern formats (WebP or AVIF), implement responsive srcset attributes, and preload above-the-fold images with link rel="preload".
- Reduce server response time: Use a CDN, implement server-side caching, and consider edge rendering for dynamic pages. Target a Time to First Byte (TTFB) under 200ms.
- Eliminate render-blocking resources: Defer non-critical CSS and JavaScript. Inline critical CSS for above-the-fold content.
Improving INP
- Minimise JavaScript execution: Audit third-party scripts. Each analytics tracker, chatbot, and recommendation widget adds to the main thread workload.
- Break up long tasks: Use requestIdleCallback and requestAnimationFrame to yield to the main thread during heavy computations.
- Use web workers: Offload non-UI tasks like data processing and analytics to background threads.
Improving CLS
- Set explicit dimensions: Always include width and height attributes on images and videos. Use CSS aspect-ratio for responsive containers.
- Reserve space for dynamic content: Pre-allocate space for ads, product recommendations, and lazy-loaded content using min-height or skeleton screens.
- Avoid inserting content above existing content: Load banners, notifications, and cookie consent bars in a way that does not push page content down.
Measuring and Monitoring
Effective CWV optimisation requires both lab and field data. We recommend a monitoring stack that includes:
- Google Search Console: For real-world (field) data aggregated from Chrome users visiting your site.
- PageSpeed Insights: For page-level diagnostics combining lab and field data with actionable recommendations.
- Real User Monitoring (RUM): Tools like web-vitals.js or Vercel Analytics capture CWV data from every visitor, giving you granular insight into performance across different devices, connection speeds, and geographies.
The Bottom Line
Core Web Vitals are not an abstract technical exercise — they are a direct lever on your revenue. For eCommerce businesses, every improvement in LCP, INP, and CLS translates to measurable gains in conversion rates, revenue per session, and customer satisfaction. The investment in performance optimisation pays for itself many times over, making it one of the highest-ROI activities any online retailer can undertake.