Core Web Vitals FAQ on data

Is Core Web Vitals about Lab data or Field data?

It is about "Field data". This means that:

  • Core Web Vitals is about real users, out in the field;
  • Chrome UX Report (CrUX) is forged from data collected via Chrome, directly from its users browsing the web;
  • It is about performance data from your very own traffic, amongst Chrome users only.

How does Google know how users are experiencing my site / shop?

Chromium users have their experiences tracked during a page visit. Once a visitor leaves the page, for example clicking to another page, Google will send the performance and UX metrics to their own servers. This is better known as the Chrome User Experience (CrUX) report.

Which visitors are excluded from Core Web Vitals?

All Chromium users (nowadays even Microsoft Edge users) have their data send to Google / CrUX. This means most real user experiences of Apple / iOS users might not be send to Google servers, as they often use Safari and Linux users might use FireFox.

Do note that users can opt-out from this setting and stop their browser from sending their experiences and thus UX and pagespeed metrics to Google servers.

How many visitors do I need for Core Web Vitals score?

Nobody knows. Tests I conducted in the past pointed out that your site needs around 400 pageviews a month per device (mobile, tablet, desktop), using Chromium to get a Core Web Vitals origin summary when using PageSpeed Insights. Do note that this might be the absolute minimum.

When a site doesn't have enough visitors, chances are you need to find other ways to rank higher. Do note: improved pagespeed will still impact conversion positively, no matter the amount of visitors or passing the Core Web Vitals assessment.

How do I know if I have enough visitors?

When doing a PageSpeed Insights test, you will always see "Lab data". "Field data", sitting on top of "Lab data", will be displayed as well. When you don't see any coloured bar charts, your webpage didn't have sufficient visitors (yet) to yield any data.

However, if your origin (domain) did have enough visitors to yield a summary, PageSpeed Insights might at least still show you an origin summary. When no "Field data" at all is being displayed, your website or webshop doesn't have enough visitors and you won't benefit from Core Web Vitals ranking factor. Do note though that improving your pagespeed, performance and UX will still impact conversion and might make you future proof in case the amount of visitors increase over time.

Will I still benefit from pagespeed without data / sufficient visitors?

Maybe, but not directly. Google won't be using lab data if your domain doesn't have sufficient field data.

You could say that a site without enough data isn't interesting enough yet (or can't be found) for a big portion of visitors. And as there are quite some ranking factors, a website has other ways to get a higher ranking already as well. Obviously, a good pagespeed/UX might actually seduce people to visit more pages, maybe ending up getting sufficient amount of data. So, pagespeed / good technical UX still matters, but in this case indirectly. On top of that, a domain or even specific page needs enough visitors to give a trustworthy representation of its Page Experience/Core Web Vitals.

What if one page doesn't have field data, but others have?

Google Search Console is already grouping pages together. Core Web Vitals will be doing the same. If one (for example newly launched) page doesn't have sufficient amount of visitors, it might fall back to and re-use the data of similar pages. If Google could not find similar pages, it will fall back to the origin summary.

Currently, one can only see if there is sufficient data for a specific page and/or origin summary. You might need to look into Google Search Console to get an idea of page grouping.

How to collect data myself when my site does not have sufficient visitors?

Hopefully, you’ll have enough traffic to get some data to see Field data within PageSpeed Insights, Google Search Console and CrUX.If not, you can still track the Core Web Vitals of your visitors and store it where ever you want. For example to Google Analytics or via Google Tag Manager. GoogleChrome published a library, including code examples on github.

You can also use tools like SpeedCurve, Akamai and Cloudflare (when already using Cloudflare for example) or cheaper though enriched toolings such as CWV Insights (disclaimer: I helped founding this).