PageSpeed Insights (PSI) reports on the performance of a page on both mobile and desktop devices, and provides suggestions on how that page may be improved.

PSI provides both lab and field data about a page. Lab data is useful for debugging performance issues, as it is collected in a controlled environment. However, it may not capture real-world bottlenecks. 

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 fast, and 50 to 90 is considered average. Below 50 is considered to be slow.

Classifying Fast, Average, Slow

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


Fast

Average

Slow

FCP

[0, 1000ms]

(1000ms, 2500ms]

over 2500ms

FID

[0, 50ms]

(50ms, 250ms]

over 250ms



Generally speaking, fast pages are roughly in the top ~10%, average pages are in the next 40%, and slow pages are in the bottom 50%. The numbers have been rounded for readability. These thresholds apply to both mobile and desktop and have been set based on human perceptual abilities.

Distribution and selected value of FCP and FID

PSI presents a distribution of these metrics so that developers can understand the range of FCP and FID values for that page or origin. This distribution is also split into three categories: Fast, Average, and Slow, denoted with green, orange, and red bars. For example, seeing 14% within FCP's orange bar indicates that 14% of all observed FCP values fall between 1,000ms and 2,500ms. This data represents an aggregate view of all page loads over the previous 30 days.

https://developers.google.com/speed/docs/insights/images/v5/field-data-chart.png

Above the distribution bars, PSI reports the 90th percentile First Contentful Paint and the 95th percentile First Input Delay, presented in seconds and milliseconds respectfully. These percentiles are selected so that developers can understand the most frustrating user experiences on their site. These field metric values are classified as fast/average/slow by applying the same thresholds shown above.

Field data summary label

An overall label is calculated from the field metric values:

·         Fast: If both FCP and FID are Fast.

·         Slow: If any either FCP or FID is Slow.

·         Average: All other cases.

Lab data

PSI uses Lighthouse to analyze the given URL, generating a performance score that estimates the page's performance on different metrics, including: First Contentful Paint, First Meaningful Paint, Speed Index, First CPU Idle, Time to Interactive, and Estimated Input Latency.

Each metric is scored and labeled with a icon:

·         Fast is indicated with a green check mark

·         Average is indicated with orange informational circle

·         Slow is indicated with a red warning triangle

 

How to use:

·        Type in your website name and click analyze