Definition

PageSpeed Insights (PSI) is a Google tool that assesses how a web page performs on mobile and desktop devices. It combines real-world field data with simulated lab data and offers suggestions for improving loading and responsiveness.

PageSpeed Insights presents two kinds of data. Field data comes from the Chrome User Experience Report and reflects how actual Chrome users experienced the page over a rolling 28-day period, including Largest Contentful Paint, Cumulative Layout Shift and Interaction to Next Paint. Lab data is generated by Lighthouse in a controlled environment using a simulated mid-tier device and network. The two can differ because lab conditions are fixed while real-world experiences vary. Field data may be unavailable for pages with insufficient traffic.

Examples

• Performance check

  A site owner enters a product URL into PageSpeed Insights and sees a 'Needs Improvement' Core Web Vitals assessment from field data alongside a Lighthouse performance score.

• Diagnosing a gap

  A developer notices the lab score is high but field LCP is poor, and investigates why real users on slower connections experience the page differently.

Sources

• Google for Developers — About PageSpeed Insights
• Chrome for Developers — Lighthouse overview

Related terms

• Core Web Vitals
  A set of three Google metrics that measure real-world page experience: loading speed, interactivity and visual stability.
• Lighthouse
  An open-source automated tool from Google that audits a web page for performance, accessibility, SEO and other best practices.
• Chrome User Experience Report
  A public dataset of real-world performance metrics collected from Chrome users, used to measure how sites are experienced in the field.
• Page Speed
  How quickly a web page loads and becomes interactive, measured by metrics such as Largest Contentful Paint, Interaction to Next Paint, and Time to First Byte.
• Largest Contentful Paint
  A Core Web Vitals metric measuring how long the largest visible content element on a page takes to render after loading begins.
• Interaction to Next Paint
  A Core Web Vitals metric measuring how long a page takes to visually respond to a user interaction, sampled across the page's lifetime.
• Time to First Byte
  A performance metric measuring the time between a request for a page and the first byte of the response arriving back at the browser.

Where QueryCatch uses this

• SEO Audit
• Page Optimisation