page speed
Also called: pagespeed, site speed, website speed, load time
Page speed is how quickly a web page loads its content and becomes usable for a visitor. Google measures it two ways: lab data from simulated tests (Lighthouse) and field data from real Chrome users (CrUX), summarized by the Core Web Vitals for loading, responsiveness, and visual stability.
Lab data vs field data
Two very different numbers both get called page speed. Lab data comes from Lighthouse running your URL in a simulated environment (a mid-tier phone on a throttled connection). It is repeatable and useful for debugging. Field data comes from the Chrome User Experience Report (CrUX), which aggregates real Chrome visits over a trailing 28-day window. Google’s ranking systems read field data, not your lab score, so the two can disagree when real visitors hit slower devices than the simulation.
Since 2020 the working definition of page speed is the Core Web Vitals, judged at the 75th percentile of real loads:
LCP(Largest Contentful Paint), loading: 2.5 seconds or lessINP(Interaction to Next Paint), responsiveness: 200 milliseconds or less. INP replaced First Input Delay.CLS(Cumulative Layout Shift), visual stability: 0.1 or less
A Lighthouse Performance score of 90 or above counts as good, but hitting 100 in the lab does not guarantee you pass in the field. Google is also explicit that page experience is one signal among many, and that a highly relevant page can still rank well with sub-par speed. Speed rarely wins a ranking on its own. It breaks ties between comparable pages and protects conversions once visitors arrive.
How it affects your traffic
Slow field-data speed rarely gets a page penalized outright, but it quietly caps results: it drags Core Web Vitals into "needs improvement," and it costs you conversions when visitors leave before the page paints. If your CrUX numbers are red while your Lighthouse score looks fine, the cause is almost always technical (render-blocking resources, oversized images, layout shift, slow server response), which is exactly the scope of a Technical SEO engagement. We measure the real field data, find what is actually slow at the 75th percentile, and fix the LCP, INP, and CLS bottlenecks that a one-off lab test misses.
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