Field data vs Lab data: Get hold of Core Web Vitals Score

Core Web Vitals were announced from the Chrome blog in early May 2021 as essential metrics for the health of a site. They are the heart of the new Web Vitals initiative, which in addition to these metrics includes a series of tools and guides to help developers meet the goal of offering a perfect user experience.

Now that you know what the new Google metrics are to improve the user experience, the next thing you probably want to know is how to measure them on your website. Before starting to talk about tools, it is important to be clear that there are two ways to measure, using field data or based on lab experiments.

So in this article, we will learn about Field data vs Lab data so that you can get hold of the CWV Score.

Let’s learn what is Field data?

What Is Field Data?

Field data is data extracted anonymously by Chrome directly from real users who visit your website, both on mobile and desktop. As indicated in the privacy policies of Google Chrome, by default the browser sends statistical data on use, crash reports, etc.

Field data is the most reliable because it offers you real information on how your website is behaving. Obviously, since it is data obtained from real visits to your website, to have it you need your site to be already published and also have traffic.

What Is Lab Data?

Laboratory data are data obtained through an experiment carried out at the time of measurement with the tool used. The advantage is they are current data so they allow you to know how your website behaves after having made a change without having to wait to collect data from real users.

Also, if your website is in the development phase and has not yet been published or is public but still does not receive traffic, this is the only way you can measure Core Web Vitals.

Tools For Field Data

You can access the field data collected by Google through three tools that they make available to you.

  • The Chrome User Experience Report
  • The Page Speed ​​Insights tool
  • The new Search Console Top Web Metrics report 

From any of them, you will be able to obtain the averages of values ​​of the three new metrics obtained from the real visits of your users.

Chrome User Experience Report (CrUX)

It is about the original source of the data and the rest of the tools that you do in drinking from it. But it is also possible to directly access your data, for example using BigQuery. The easiest thing is to do it through the connector created for Google Data Studio by the team in charge of CrUX, in this way we can obtain a dashboard with all the information on our website.

Of course, the data obtained with this dashboard will be the averages of the values ​​for the entire data source, that is, our domain (or subdomain) accessing through a specific protocol. 

Page Speed ​​Insights

Page speed insights provides us with quick access to know the values ​​of the Core Web Vitals of a specific URL, as well as the aggregated data of the entire origin. In addition, it provides us with both field and laboratory data.

In reality, this tool does not have its own data, but accesses the data from the Chrome UX report to obtain the field data and uses Lighthouse to perform an experiment and show us the laboratory data.

Search Console Report

Since the end of May, we can find this new report in Search Console, which has replaced the performance report that it provided before.

Again, it is data that comes from the Chrome user experience report, the advantage, in this case, is that you will have a global vision of how many URLs on your site are good, fair, or bad and it will point out the problems detected in each one so you can fix them.

At first, it shows you two timelines in which you can see how the URLs of your site have evolved, segmenting the data between mobile and computer. Next to each graph, there is a link that allows you to access a more detailed report to see what problems have been detected and by clicking on each of them you can see which URLs it affects. Of course, it will show you some examples but it will group those URLs that I considered similar (for example, blog posts, on the one hand, categories on the other, etc.).

Tools To Perform Lab Data

If you want to obtain current/Lab data by experimenting to know the values ​​of the Core Web Vitals at the time of the check, you can use the following tools:

  • Lighthouse
  • Google Chrome Developer Tools
  • Web Page Test

The first two are tools provided by Google, while Web Page Test is an open-source tool but Google itself offers it as a valid option to obtain this data.

It is important to bear in mind that since it is laboratory data obtained through an automated experiment in which a real user does not intervene, they will not provide the FID. As an alternative, if you do not have field data, Google proposes to use the TBT instead, that is, the  Total Blocking Time or total blocking time.

Without going too far, the TBT is the sum of the periods in which the main browser thread remains blocked from when the page starts to be painted until it is fully interactive. Always these blocks are greater than 50 ms and that time will be subtracted from the time that the block lasts when adding them.


Lighthouse is a tool created to audit websites, there are multiple ways to access it, but the simplest is through Google Chrome. Initially, it was necessary to install a Chrome extension, but in the latest versions, it is integrated as part of the DevTools or development tools.

Chrome Developer Tools (Chrome DevTools)

In addition to being able to use them to access the Lighthouse reports, in the Performance tab, you can see in detail the behavior of your website during loading, analyze which tasks are blocking the interactivity of the browser for the longest time, if any resource takes too long to load, etc.

Web Page Test is a tool that allows you to analyze the performance of a website by configuring aspects such as the place from which the connection is made, the browser, or the type of internet connection used. In addition, it allows you to record a video of the behavior during loading that can be very useful to detect some problems at a glance, such as a large element that is taking time to load and causes you to have a bad LCP.

We could go much deeper into the information that each of these tools offers us and how to use it to optimize a website, although that is not the purpose of this article.


To make your website Core Web Vitals error-free, this Lab Data vs field Data article can help. Also to get hold of CWV Score, this Lab Data vs field Data comparison can help you to find other hidden Core Web Vitals errors and fix them.

Google has been moving towards giving more and more weight to the user experience when it comes to giving more or less visibility to a page. So make your website’s user experience brilliant.

I hope this Lab Data vs field Data article can help you to get the best Core Web Vitals score. If you have questions or suggestions, don’t hesitate to share your thoughts in the comment box.

Leave a Comment

Your email address will not be published. Required fields are marked *