What is the Google PageSpeed Insights report?
Google PageSpeed Insights (PSI) is a free tool that analyzes the performance of a web page on both mobile and desktop devices. It provides a detailed report based on lab data (simulated performance) and field data (real-world performance).
What do Core Web Vitals measure?
Core Web Vitals are a set of performance metrics that Google developed to help site owners measure a webpage's overall user experience. The three metrics are based on field data, which means they measure how real-world users experience your website:
Largest Contentful Paint (LCP): Measures the loading performance of the largest content element visible on the page.
Interaction to Next Paint (INP): Quantifies responsiveness and interactivity.
Cumulative Layout Shift (CLS): Measures the visual stability of the page by quantifying unexpected layout shifts.
What does PSI's Performance score measure?
PageSpeed Insights' Performance Score is based on lab data, which refers to performance metrics gathered in a controlled environment using predefined conditions (such as specific device and network settings).
Lab data, also known as synthetic data, allows for consistent and repeatable measurements, making it ideal for debugging performance issues.
Important: Your Performance score doesn’t reflect how real visitors experience your website.
Why your Core Web Vitals matter more than your PSI score
Core Web Vitals are crucial indicators of your site's real-world user experience and an official Google ranking factor. Failing any of the three metrics—LCP, INP, or CLS—means visitors are experiencing slow load times, poor responsiveness, or visual instability each time they visit your website.
If you’re failing your Core Web Vitals, your site’s performance and user experience suffer, resulting in:
Lower search engine rankings
Higher bounce rates
Fewer conversions
In contrast, the PSI Performance score is based on lab data and doesn't reflect actual user experiences. Achieving a perfect PSI score doesn't guarantee excellent performance. Therefore, prioritizing Core Web Vitals is essential for ensuring a top-notch user experience and optimal performance.
Important: A perfect 100 PSI score doesn’t necessarily translate to an excellent user experience. Passed Core Web Vitals does.