Google considers a Largest Contentful Paint (LCP) of 2.5 seconds or less as “good.” For many businesses, this benchmark has become the ultimate performance goal. Once a site reaches that threshold, optimization efforts often slow down.
However, this widely accepted benchmark is based on aggregated data collected from millions of websites. While it serves as a universal guideline, it doesn’t necessarily reflect how visitors interact with an individual website.
In research conducted by web performance expert Tammy Everts, who analyzed one month of Real User Monitoring (RUM) data from ten leading online retailers, the findings suggest that Google’s recommended LCP threshold may not represent the point where websites achieve the best user engagement. Instead, the study highlights the value of using site-specific performance data to identify optimization targets that align with actual user behavior.
Why Google’s Recommended LCP Threshold May Not Be Enough
Google’s 2.5-second LCP recommendation defines what is generally considered acceptable across the web.
However, every website serves different audiences, products, and user expectations. As a result, the performance target that works best for one business may not deliver the same results for another.
The research does not question the importance of Core Web Vitals. Instead, it explores whether Google’s recommended thresholds should automatically become the optimization target for every individual website.
Performance correlation charts repeatedly demonstrate a consistent trend:
- As Largest Contentful Paint (LCP) becomes slower, bounce rates increase.
- Slower user-centric metrics such as Interaction to Next Paint (INP) are also associated with reduced user engagement.
- Better page performance generally aligns with lower bounce rates and stronger conversion potential.
Research Overview
To examine whether Google’s threshold aligns with real business outcomes, one month of Real User Monitoring (RUM) data was collected from ten leading online retailers.
For every retailer, a performance correlation chart was created that compared:
- Session-level Largest Contentful Paint (LCP)
- Bounce rate
This approach made it possible to identify the point where each site’s bounce rate reached its lowest level.
Here’s a cleaner version that removes all references to chart colors while preserving the original meaning:
What Is a Performance Correlation Chart?
A performance correlation chart is a data visualization that shows the relationship between website performance metrics and business or user engagement metrics.
Rather than measuring technical performance alone, it helps identify how changes in page speed influence real user behavior, such as bounce rate or conversion rate.
How the Chart Works
The chart groups user sessions into performance-based cohorts using metrics such as:
- Largest Contentful Paint (LCP)
- Start Render
- Interaction to Next Paint (INP)
- Other page rendering metrics
Each performance cohort is then compared against a business or engagement metric to reveal how user behavior changes as website performance improves or declines.
For this research, bounce rate was used as the primary engagement metric. It was chosen because:
- It is captured by default in most Real User Monitoring (RUM) tools.
- It does not require additional instrumentation.
- It serves as a reliable directional indicator of user engagement.
The research also notes that when a strong relationship exists between page performance and bounce rate, a similar relationship often appears with conversion rate, making bounce rate a useful proxy for evaluating performance impact.
Two Key Markers Used in the Research
Each performance correlation chart highlighted two important reference points.
1. Google’s “Good” LCP Threshold
Every chart included Google’s recommended benchmark.
Annotation:
2.5s = Good
This marks Google’s official passing threshold for Largest Contentful Paint under Core Web Vitals.
2. Site-Specific Ideal LCP
Each chart also identified the performance level where bounce rate reached its lowest point.
For the first retail website, the chart showed:
- 0.5-second LCP
- 42% bounce rate
- Marked as the site’s ideal performance point
This optimal result occurred well below Google’s recommended threshold.
Key Findings from the Research
Across all ten leading online retailers, the best bounce rate consistently occurred when Largest Contentful Paint fell between 100 milliseconds and 1 second.
For Retail Site 1, the ideal result was:
- LCP: 0.5 seconds
- Bounce Rate: 42%
This represents a performance level approximately 2 seconds faster than Google’s “good” benchmark.
The charts visually indicate this optimal range with the annotation:
“You may need to be here.”
What This Means for Website Performance
Google’s Core Web Vitals thresholds are designed as universal recommendations rather than individualized business targets.
The findings suggest that meeting Google’s benchmark does not necessarily mean a website has reached its optimal user experience.
For the retailers analyzed:
- Google’s threshold identified acceptable performance.
- The lowest bounce rates occurred much earlier, between 100ms and 1 second.
This indicates that businesses seeking stronger engagement may benefit from identifying their own performance targets instead of relying solely on Google’s general recommendations.
Focus on Business Outcomes, Not Just Passing Scores
Achieving a passing Core Web Vitals score is valuable, but it may not represent the point where visitors are most likely to remain engaged.
The research suggests that organizations should:
- Build performance correlation charts using Real User Monitoring data.
- Measure how page speed relates to bounce rate.
- Identify where their own bounce rate curve begins to flatten.
- Use that point as the site’s performance target.
For many websites, that optimal range may fall between 100 milliseconds and 1 second LCP, regardless of Google’s broader benchmark.
Conclusion
Google’s 2.5-second Largest Contentful Paint threshold remains an important industry benchmark, but it is based on aggregated web data rather than individual website behavior.
Analysis of ten leading online retailers found that the lowest bounce rates consistently occurred at significantly faster load times, generally between 100 milliseconds and 1 second.
Instead of treating Google’s benchmark as the finish line, businesses can use performance correlation charts and Real User Monitoring data to identify the loading speed that delivers the strongest user engagement for their own website.
FAQS – Core Web Vitals Thresholds
Luv Nagpal 