How to measure your Core Web Vitals performance

Knowing where to start in terms of optimizing your site for Core Web Vitals can feel overwhelming! Just as any smart journey starts with mapping out where you’re at and making a plan to get where you want to go,...

By Marie King

Knowing where to start in terms of optimizing your site for Core Web Vitals can feel overwhelming! Just as any smart journey starts with mapping out where you’re at and making a plan to get where you want to go, your starting point is to assess your current performance. 

This guide is designed to help you and your developer gauge how your site and pages are currently performing in terms of Core Web Vitals so you can make a plan to start optimizing.  

Here’s what we’ll go over in this guide: 

  • How to measure Core Web Vitals
  • Lab data vs field data: what’s best for tracking your Core Web Vitals performance?
  • Data available from different performance tools
  • What metrics matter and what scores to aim for

Keep in mind, Core Web Vitals are meant to improve user experience — always look at your data through the lens of your readers’ experience. 

Let’s jump in and break it all down!

How to measure Core Web Vitals

Not only did Google give advanced warning of this algorithm update, but they also provided helpful tools to use as you work through improvements on your site. 

There are actually a lot of tools available for measuring site performance and user experience, but not every tool has every Core Web Vitals metric (yet).

Here’s a handy chart showing which tools have what data available:

It’s important to note that none of these tools or the scores they deliver are exactly what Google uses internally to rank results in search result pages. 

The goal of these tests and scores is to give publishers clear milestones, along with guidelines and various tool kits, to address usability issues that may be impacting your audience’s experience on your site.  

Lab data vs field data: what’s best for tracking your Core Web Vitals performance?

Before we dig into how to measure and track your vitals, let’s address the difference between lab and field data, as different tools will give you different results based on this distinction.

  • Lab data is simulated data. It uses probabilities and approximations to simulate reader activity. 
  • Field data, on the other hand, is “real-life” data. It’s collected from actual Chrome browser users who visit your site. 

Benefits of lab data

While field data might sound better because it comes from real people, there are some advantages to using lab data.

  • First, experiences with the page are wildly different from user to user, from device to device, from browser to browser. These varying conditions can result in a high spectrum of scores, and these scores can also change as you navigate pages. Lab data can help provide a more stable, straightforward way to analyze your site to spot issues. It’s much more replicable — you can run the exact same test a year or two down the line.
  • Lab data allows you to test your website during the development phase before you’ve released something to users.
  • Lab data can help you catch performance regressions and issues before they happen.

Benefits of field data

Field data also has some great advantages:

  • Network conditions and device processing power can differ for your users, so field data takes that into consideration.
  • Your site is dynamic. Sometimes elements will load (like ads) and sometimes not — field date gives you the true experience.
  • Browsers and readers’ devices behave differently than your test device.
  • It measures performance where it actually matters: lab is just a proxy to help us get here, in front of your readers.

What data is available in which tool?

Here’s a helpful chart of the tools Google recommends, showing what data is available on each platform:

Something else to pay attention to: tools might differ in terms of the date range for when data is pulled as well as the level of detail in the report. 

If you’re seeing discrepancies in Core Web Vitals metrics across different tools, 1) check the date range the tool uses and 2) check whether it’s reporting field data or lab data.

How to get access to page-level data

According to Google, “Core Web Vitals thresholds are assessed at the per-page level” so how can a publisher get access to page-level data (i.e. Core Web Vitals scores for a specific post vs. your entire site)? 

You can access more granular Core Web Vitals scores in 3 ways: 

  • Via the CrUX report/PageSpeed Insights — though be aware that the page needs to reach CrUX’s hidden reporting sample threshold, which means you may only be able to see page-level data for posts that receive high traffic.
  • Google Search Console reports Core Web Vitals data in URL groups, which gives you a sample of pages with similar HTML structure. Depending on the number of URLs on your site and how Google decides to group them, you may be able to get a more granular look here.
  • You can also collect Core Web Vitals using a 3rd-party tool like CloudFlare or Akami.

What metrics matter? And what score should you try to achieve?

All of the metrics matter… to some degree.

We are still unsure as to how much each of the metrics is weighted in the algorithm, whether FID, LCP, and CLS are equally important or some are more important than others.

For example, if you look at the way Lighthouse uses the metrics to calculate overall scores, they only weigh CLS at 5% whereas LCP contributes to 25% of their score. 

However, we can’t confirm that Lighthouse reflects the Google search algorithm weightings, so for now, we recommend making your best, reasonable efforts to improve all three of them. 

Tackle the worst first. The Core Web Vitals that matter most for your site optimization are likely the ones where your site is doing the worst. If you’re seeing poor scores, start there.

Focus on “passing”. If you’re very close to “passing” a particular Core Web Vital metric with a good score, it may be most beneficial to focus your efforts there first.

Don’t get hung up on “perfect”. You’ll likely see fewer benefits from focusing on improving Core Web Vitals where your site is already seeing a score in the range Google deems “good”.

Your first and most important goal is to pass that “good” threshold before making improvements above and beyond.

Outrun the bear: be better than the competition

You want to be doing as well as you can — but mostly you want to be doing better than your competitors.

And where this truly matters is at the page level (where you’re fighting to rank for a topic in Google) vs. at the site level.

Look at Core Web Vitals and other scores primarily on your content pages, not your homepage. 

Each page may have very different scores and you want to optimize for the pages you want to rank highest for the most competitive search terms. 

You can use the ChromeDev, PageSpeed Insights,, and/or Lighthouse reports to analyze your competition. 

One place to start is page-level performance.Find your top-earning pages, then do a Google search to see the pages you’re competing with, and run those URLs through the tools to see what their scores are. 

  • Is your performance similar to the competition or is there a big difference? 
  • Are you failing in a certain Core Web Vitals metric that your competition is passing? 

This is a helpful place to start as you figure out what you need to tackle. Again, aim to get a passing score in all the metrics before you start to work toward a really great score. 

Look beyond the score: the ultimate goal is user experience

It’s easy to get bogged down in the numbers, but don’t forget to look at the big picture and consider the value of what you’re offering to your readers. 

You could serve a blank page that gets perfect web vitals scores, but that wouldn’t be useful to anyone. The first priority should always be to publish outstanding material that serves user needs. 

Then, when you optimize your site to make sure their journey through your content is a smooth one, you’re sure to succeed! When you create great content that is easy to consume, you make the internet a better place for everyone — publishers, advertisers, and readers.