PageSpeed Insights
What is PageSpeed Insights?
PageSpeed Insights (PSI) is a free Google tool that reports how a page performs, using two kinds of data. The top section shows field data from the Chrome User Experience Report: real visitors’ Core Web Vitals over the last 28 days. The lower section runs Lighthouse and shows a lab performance score with diagnostics.
You enter a URL and get separate results for mobile and desktop. Field data appears only when Google has enough visits for that URL or origin; small sites may see only the lab section. PSI also has an API, which many tools use to test pages in bulk.
Why PageSpeed Insights matters for SEO
PSI is the quickest way to see whether a page passes Core Web Vitals for real users, which is what Google’s ranking systems use, and to get a lab report explaining why it might not.
Read the two halves for what they are. The field assessment (“passed” or “failed”) is the one that matters for page experience. The 0–100 performance score is a single simulated test that varies from run to run, and chasing a perfect score often brings little benefit once the field metrics are good.
How to use PageSpeed Insights
- Enter a URL at pagespeed.web.dev and start on the mobile tab, since most sites have more trouble there.
- Check the Core Web Vitals assessment in the field data. Switch between “This URL” and “Origin” to see whether the problem is the page or the whole site.
- Scroll to the Lighthouse diagnostics and look at the LCP element, render-blocking requests, long main-thread tasks and layout shifts.
- Fix the biggest causes, then retest the lab result. Field data takes up to 28 days to update.
PageSpeed Insights FAQ
Why does PageSpeed Insights say “no data”?
The page or site does not have enough real Chrome visits in the Chrome User Experience Report. You still get the Lighthouse lab test.
Is a PageSpeed score of 100 necessary?
No. What counts for search is passing Core Web Vitals in field data. A lab score in the 80s with good field metrics is fine.
Related SEO terms
Lighthouse is Google’s open-source tool that tests a page in a lab and scores its performance, accessibility, best practices and SEO.
Core Web Vitals are Google’s three metrics for real-world page experience: Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift.
Page speed is how quickly a page loads, shows its content and responds to input. Google measures it mainly through Core Web Vitals.
Largest Contentful Paint (LCP)
Largest Contentful Paint (LCP) is a Core Web Vital that measures when the largest image or text block in the viewport appears. Good is 2.5 seconds or less.
Google Search Console is Google’s free tool that shows how your site performs in Google Search and flags indexing, security and spam problems.