John Mueller answered a question at the SEO Office-hours conference about why the core web vitals score keeps changing, even when the web page itself doesn’t.
There are two core network vital signs scores:
- Field data
These are core web vital signs scores recorded from actual visitors to websites in the real world.
The purpose of the field data is to show the real user experience of actual site visitors for a given site. - laboratory data
These are the core network vital signs scores generated by the simulated visits. A bot from Google Lighthouse will visit the page under test using a user-agent identified as Chrome/94.0.4590.2, and the algorithm will simulate the visit being on a mobile phone and a restricted internet connection. Collect page load information and generate artificial core network vital signs scores. The purpose of laboratory data is diagnosis. Lab Data helps website publishers or SEOs troubleshoot web page performance. The information provided by Lab Data will help publishers or SEOs understand what is causing web page slowdowns and provide tips on how to fix them.
Screenshot of John Mueller discussing Core Web Vitals scores
Lab data was generated using Google’s Lighthouse tools.
In fact, the bot that visited the website used the word Lighthouse in the user agent when generating the core Web Vitals score for the lab data.
According to the official introduction Lighthouse webpage:
“Lighthouse is an open source automation tool for improving the quality of web pages.
…it audits performance, accessibility, progressive web apps, SEO, and more.
You can run Lighthouse in Chrome DevTools, from the command line, or as a Node module. You give Lighthouse a URL to audit, it runs a series of audits against that page, and then generates a report on how well the page performed.
From there, use failed audits as an indicator of how to improve your page. Each audit has a reference document explaining why the audit is important and how to address it. “
Core Web Vitals scores keep changing
The questions answered by John Mueller did not specify whether it was about field data or laboratory data.
The person asking the question simply asked when the core network vital signs scores stopped changing, without specifying field or laboratory data.
Mueller answers this question from the perspective of Lab Data, which is based on the core network vital signs scores of real-world visitors.
Here is the question being asked:
“When will the core network vital signs provide stable and correct information?
It keeps changing without changing any data on the website. “
Core Web Vitals scores are affected by random factors
The answer centers on the randomness of the data used to generate the core Web Vitals field data.
John Mueller replied:
“So, I think it might be a side effect of how core Web vitals and page experience updates are handled.
This is where I would try to find these details to learn more about the field data…how the data that the user actually sees plays a role in that.
This is if users from different backgrounds, different locations, and different device types visit your page, you may see some fluctuations over time. “
Internet speeds vary
Fast servers and fast websites are only part of getting a high Core Web Vitality score, it’s the only part that is controlled by SEO or the website publisher.
As John Mueller said, there are many other factors that can affect core network vital signs scores, many of which are not always controllable.
Even if a website is hosted on a fast dedicated server, network congestion, outdated mobile phones used by website visitors, and poor mobile data connections can significantly impact the core Web Vitals performance of an otherwise fast website, reducing rather than getting good cores on live data Network vital signs score.
Some website visitors may be using newer phones with powerful processors running on newer 5G networks. Visitors to this site will generate high scores on the core Web Vitals field data.
Things like network latency (how slow the entire internet is at any given moment) also affects real-world field data and simulated lab data.
Therefore, even though the lab data is not a real visitor, an actual Chrome-based bot will visit the web page being tested over the Internet. This also affects the simulated lab data scores.
Google’s Web.dev site posted an explainer of why field data is always changing, not the same every month.
web development explain like this:
“The most important thing to understand about field data is that it’s not just a number, it’s a distribution of numbers. That is, for some people visiting your site, it might load very fast, and for others For example, it might load very slowly.
this Field data For your website is a complete collection of all performance data collected from your users.
For example, the CrUX report shows the distribution of performance metrics for real Chrome users over a 28-day period. If you look at almost all CrUX reports, you will find that some users visiting the site may have a good experience, while others may have a poor experience. “
Whether you’re at a testing site for lab data or viewing real-world field data, core network vital signs scores fluctuate and may not provide a consistent score from month to month.
Citation
When will the Core Web Vitals score stabilize?
Watch John Mueller answer questions at 19:05 minutes:
