Mobile and Desktop Web Page Performance

Make your web pages fast on all devices.

Performance Score

At the top of the report, PSI provides a score which summarizes the page’s performance. This score is determined by running Lighthouse to collect and analyze lab data about the page. A score of 90 or above is considered good. 50 to 90 is a score that needs improvement, and below 50 is considered poor.

Real-World Field Data

When PSI is given a URL, it will look it up in the Chrome User Experience Report (CrUX) dataset. If available, PSI reports the First Contentful Paint (FCP), First Input Delay (FID), Largest Contentful Paint (LCP), and Cumulative Layout Shift (CLS) metric data for the origin and potentially the specific page URL.

Classifying Good, Needs Improvement, Poor

PSI also classifies field data into 3 buckets, describing experiences deemed good, needs improvement, or poor. PSI sets the following thresholds for good / needs improvement / poor, based on our analysis of the CrUX dataset:

Good Needs Improvement Poor
FCP [0,1000ms] [1000ms,3000ms] over 3000ms
FID [0,100ms] [100ms,300ms] over 300ms
LCP [0,2500ms] [2500ms,4000ms] over 4000ms