PageSpeed Insights

PageSpeed Insights is a public tool introduced by Google. It can be found via The purpose of PageSpeed Insights is to show users both a score from synthetic testing and an overview of data collected from real user experiences.

Even back in the days, it showed both field data (if available) and lab data. However, the lab data section wasn't build on top of Lighthouse yet.

Below is a screenshot from before the moment PageSpeed Insights started using Lighthouse (pre November 2018). This screenshot is showing actual distributions of First Contentful Paint and Dom Content Loaded.

Lighthouse era

As of November 2018, PageSpeed Insights adopted Lighthouse (version 4 by then). This came with an improved set of opportunities and recommendations. As PageSpeed Insights is using for lab data scoring purposes, a pagespeed is always tested under fixed conditions.

This is very convenient when working with a team, or sharing results with your client. Chances are the score won't fluctuate that much per test. However, when teams end up using the Lighthouse test in their browser instead of PageSpeed Insights, it often happens that the performance score will be very healthy, while PageSpeed Insights is showing a different score.

Field data

When running a PageSpeed Insights test, PageSpeed Insights might show you data collected from real users, in other words: field data. Below is a screenshot after running a test for the domain, showing that Amazon really is on top of pagespeed:

In a nutshell, this is what we're seeing:

  • This URL vs Origin
    Mobile data for At the right, we can see a toggle for "This URL" and "Origin". When there is no data for a specific URL, then this toggle will automatically fall back to and show origin data when there is a sufficient amount of data. A lot of people are overlooking this toggle, and end up drawing wrong conclusions;
  • Core Web Vitals assessment passed
    As -at time of writing- only the top three metrics are part of Core Web Vitals, Amazon's origin data is passing Core Web Vitals. This is beneficial towards the Page Experience ranking signal.
    If you aren't passing this assessment, then be sure to read our blog post covering Core Web Vitals assessment failed.
  • Metrics and percentiles
    Per Web Vitals metric, you will see the experience at the 75th percentile. The horizontal grouped color bars are representing the good, moderate and poor distribution.
    You can get more data by toggling the "Expand view" at the right.
  • Characteristics
    In the block at the bottom, you see the characteristics and limitations of this data.

Lab data

Unlike field data, PageSpeed Insights will always show you lab data (unless an error occured, such as your server, CDN or CMS blocking the test). This will look as following:

In a nutshell, this is what we're seeing:

  • Categories
    Just like a Lighthouse test that was run from your DevTools, PageSpeed Insights' Lighthouse result will also show 4 categories. When it comes to pagespeed optimization, the "Performance" category is important here.
  • Overall score
    Below those categories, you get to see the details of the first category, which is the "Performance category". It is showing a single overall score based on the scores for the individual metrics.
    Do note though that looking at a single score can be misleading. When a single metric starts to fluctuate, your score will look different right away without telling you why.
  • Screenshot
    A screenshot of the webpage is aligned to the right. This can sometimes be convenient to see if your cookie notice was loaded or not, skewing potential (often LCP) outcomes.
  • Metrics
    Below that, you get to see 5 metrics. This used to be six and might change to six at one point in the future. However, Time to Interactive isn't part of the Lighthouse score calculation anymore and was recently removed from the interface as well.
    Continue reading at Web Vitals metrics to learn more about these metrics and how they can be different than your Core Web Vitals.
  • Characteristics
    In the block at the bottom, you see the characteristics and limitations of a Lighthouse test.

Links that can be found in a Lighthouse report in PageSpeed Insights are as following:

Who can use this tool?

As the tool can be found via a public URL and doesn't require login to use the tool, it can be used by anyone. As it's showing both field data and lab data, it's a convenient tool for many people from different roles.

However, it's aggregated and delayd data, and doesn't offer a timeline. Filter capabilities are missing as well, making it very hard to troubleshoot from a pagespeed optimization perspective. Google Search Console already gives a bit more guidance.

Continue reading about PageSpeed Insights

PageSpeed Insights keeps evolving. During a more recent UI update, the position of the lab data and field data got switched. Nowadays, the Core Web Vitals data can be found at the top, while the Lighthouse results can be found at the bottom.

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