With the launch of Yottaa’s new Web Performance Index, we’re uncovering fresh insights into how site speed and performance shapes shopper behavior. One of the most compelling findings: passing Google’s Core Web Vitals isn’t enough to maximize revenue. In this post, we’ll share the initial data showing why the real gains come from going beyond “good” scores.
All data cited is from the Yottaa Web Performance Index as of September 23, 2025. The Index updates daily, so figures may shift over time.
Passing Isn’t Performing
For many eCommerce teams, achieving a “passing” score on Google’s Core Web Vitals feels like a milestone. And in some ways, it is: passing ensures your site has a baseline user experience and visibility in search rankings. But new insights from the Yottaa Web Performance Index (WPI) show that passing Core Web Vitals isn’t the finish line. It’s the starting line.
Going beyond Google’s thresholds is where brands unlock real business growth. Our latest data proves that when teams shave seconds or even milliseconds off performance, conversions climb.
LCP: The Conversion Gap Between 2.5s and 1.3s
Google’s bar for Largest Contentful Paint (LCP) is 2.5 seconds. Hitting that score means your site passes in the eyes of search algorithms. But in practice, 2.5 seconds is far from optimized.
According to the WPI, sites that reduce LCP from 2.5s down to 1.3s see conversion rates rise from 1.50% to 2.25% — a nearly 50% relative lift. That’s the difference between simply being search-ready and being revenue-optimized.
INP: Milliseconds Make Millions
Interaction to Next Paint (INP) tells a similar story, only this time the margins are even smaller. Google considers anything under 200ms good. But the WPI shows peak conversion occurs much closer to 50ms.
At 200ms, conversion rates average 3.91%. Drop to 50ms, and they climb to 4.44% — a ~13.5% relative lift. That’s just 150 milliseconds, nearly imperceptible to the human eye. But across a high-traffic eCommerce site, those invisible milliseconds equate to millions in potential revenue.
Speed, Bounce, and Revenue Are Interlinked
Site load time has always been a critical factor in shopper experience, and the WPI data underscores just how high the stakes are.
When a page loads in 2 seconds, conversion peaks at 2.05%. Add just 1 more second (3s load), and conversion drops to 1.59%. Bounce rates also spike by more than 12 percentage points, from 45.63% to 57.81%.
The message is clear: site speed is not just a technical metric. It’s a direct driver of revenue.
CLS: A Nuanced Vital With Real Consequences
Cumulative Layout Shift (CLS) paints a slightly different picture. Conversion rates stay flat at 1.99% whether CLS is a passing 0.10 or a “needs improvement” 0.15.
Does that mean CLS doesn’t matter? Not quite. While CLS may not show a direct conversion correlation in this dataset, it still plays a major role in UX — and Google treats it as a pass/fail factor. Failing CLS can jeopardize search visibility, reducing traffic before shoppers even land on your site.
See Where You Stand
Core Web Vitals are essential, but they are not the ceiling. They’re the baseline. Passing them ensures visibility and a minimal user experience, but real business growth comes from pushing beyond Google’s thresholds.
The latest WPI data makes it clear: every second — and even every millisecond — matters for eCommerce revenue.
The Yottaa Web Performance Index is a continuously updated resource that lets you explore how your site stacks up against peers across industries, platforms, and devices. Updated daily, it provides the context retailers need to connect speed improvements with business outcomes. Explore the Web Performance Index now.
