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SEO

PageSpeed Insights

Free

PageSpeed Insights is Google's official web performance testing service for individual URLs. It combines available Chrome User Experience Report field data with a Lighthouse lab analysis, reporting Core Web Vitals and diagnostic opportunities for mobile and desktop contexts without guaranteeing that every recommendation will improve real-user outcomes. It is best for developers, SEO teams, and site owners investigating performance regressions, prioritizing measurable fixes, and comparing lab findings with production monitoring.

Optimizationweb performancecore web vitalslighthousepage speed

What it does

PageSpeed Insights tests a single URL and returns two distinct views of its performance. Field data, when available, comes from the Chrome User Experience Report and shows how real visitors experienced the page over the previous 28 days, including the Core Web Vitals: Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift. Lab data comes from a Lighthouse run in a controlled environment, producing a performance score and specific diagnostics such as render-blocking resources, oversized images, and unused JavaScript, each with estimated savings. The distinction matters because Google's ranking systems use field data, while lab diagnostics are the to-do list for improving it.

Where it fits

PageSpeed Insights operates at the optimization stage, turning the page experience signals that Search Console flags into specific engineering work.

Core features

  • Core Web Vitals field data from real Chrome users
  • Lighthouse lab analysis with a performance score
  • Specific diagnostics with estimated improvement impact
  • Separate mobile and desktop assessments
  • Free API for automated and bulk testing

Best for

  • Developers diagnosing slow pages with concrete fix lists
  • SEO teams monitoring Core Web Vitals compliance
  • Site owners verifying performance after a redesign or migration

Beginner notes

  1. Judge the site by field data, not the lab score; a mediocre Lighthouse score with green Core Web Vitals means real users are fine.
  2. Lab results vary between runs, so do not chase small score changes; focus on the named diagnostics with large estimated savings.
  3. Popular pages may show field data while quieter ones do not, because CrUX requires a minimum traffic threshold per URL.
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Technical SEO

Technical SEO helps search engines crawl, understand, render, and index a website.

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