Google On Why Google Search Console LCP Is Not Wrong

10/03/25
Source: Search Engine Roundtable by barry@rustybrick.com (Barry Schwartz). Read the original article

TL;DR Summary of Why Google Search Console Reports Bad LCP When Individual URLs Are Fine

Google Search Console (GSC) and Chrome UX Report (CrUX) measure Core Web Vitals differently, which can cause apparent contradictions. GSC often highlights popular, cached pages with faster load times, while uncached “long tail” pages load slower and impact overall LCP metrics. To improve, focus on optimizing uncached page load speeds rather than relying solely on caching. Testing with random URL parameters can reveal true uncached performance.

Optimixed’s Overview: Understanding the Discrepancy Between Google Search Console LCP Scores and Individual URL Performance

Core Web Vitals and Measurement Differences

Google Search Console’s (GSC) Core Web Vitals report may indicate poor Largest Contentful Paint (LCP) scores while individual URLs appear fine. This stems from the different methodologies used by GSC and Chrome UX Report (CrUX):

  • CrUX measures the 75th percentile of actual page loads, aggregating user data across many sessions.
  • GSC often samples popular pages that surpass data thresholds, which tend to be cached and faster.

The Popular vs. Long-Tail Page Load Speed Divide

Ecommerce and large sites experience a traffic distribution where popular pages receive most views and are heavily cached, resulting in faster load times:

  • Popular pages: Cached in various layers (database, CDN edges), showing better LCP scores in GSC examples.
  • Long-tail pages: Less frequently visited, often loaded uncached, leading to slower LCP that affects overall metrics.

This caching bias can mask slower loads visible only in the aggregate CrUX data.

Improving Uncached Page Performance

Since caching can only go so far, optimizing the speed of uncached pages is essential. Recommended strategies include:

  • Testing page speed with random URL parameters (e.g., ?test=1234) to simulate uncached loads.
  • Comparing these uncached tests with cached runs to identify performance gaps.
  • Aiming for uncached LCP times under 2.5 seconds as a baseline.

Additional Considerations

URL parameters used in campaigns (like UTM tags) can cause cache misses and slower loads. Upcoming standards such as No-Vary-Search allow sites to specify which URL parameters can be ignored by caches, improving caching efficiency for parameterized URLs.