Core Web Vitals and WordPress SEO

In May 2020, Google announced that page experience measurements called “Core Web Vitals” would become a ranking factor in Google Search. Later last year, they announced that this would happen in May 2021 – a year after the initial announcement.

As we write, a lot of website owners are working to improve their Core Web Vitals scores in the hope of improving ranking in the world’s most popular search engine when this change is introduced. Many others are working in fear of losing the ranks they currently enjoy.

core web vitals

Core Web Vitals are measurements of page experience that will be combined with existing search signals including mobile friendliness, safe-browsing, HTTPS-security, and intrusive interstitial guidelines to give a page experience rank for pages.

Pages with an excellent page experience should see improved ranking and in their article Timing for bringing page experience to Google Search, Google also announced that it will introduce a visual indicator to identify pages that have met all of the page experience criteria. This is expected to be a symbol that appears in a page’s snippet in search results. Obtaining this logo should increase click-thru and therefore traffic for pages.

What do Core Web Vitals measure?

Core Web Vitals are calculated using data collected by the Chrome browser. You can find your scores, page by page, using PageSpeed Insights (also available in SEOPress PRO) and Search Console’s Core Web Vitals report.

A page must have been visited a certain number of times by Chrome users over the last 28 days to register a score. If a page has too little data, Page Speed Insights will show the message “The Chrome User Experience Report does not have sufficient real-world speed data for this page.”

If there is enough data, the PageSpeed Insights tool will show the results for 4 measurements: First Contentful Paint (FCP), First Input Delay (FID), Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS). Only the last 3 are part of Core Web Vitals.

field data core web vitals

Based on these 3 results, a page either passes or does not pass the core web assessment. It is believed that passing the assessment is the only factor that will have a positive effect on ranking. There is no nuance on how close you got, how good you were with one of the three criteria, etc.

Here is the detail of what each of the 3 scores actually measures and how to pass the test:

  • Largest Contentful Paint (LCP): measures loading performance up to the point where the page is sufficiently visible. To provide a good user experience, LCP should occur within 2.5 seconds of when the page first starts loading. Over 4 seconds is considered poor. In the example above, 66% of users had a good LCP experience (less than 2.5 seconds), 21% had a poor experience (over 4 seconds). The average score is 3.5 seconds. The average score is irrelevant for the test, however, the page will pass the test if over 75% of users experienced a good result. In this case, with only 66% of good results, the site did not obtain a good enough result for LCP and for this reason did not pass the Core Web Vitals assessment.
  • First Input Delay (FID): measures interactivity, meaning the time a user had to wait for the site to respond after clicking on a link or button. To provide a good user experience, pages should have a FID of less than 100 milliseconds. Over 300 milliseconds is considered poor. The site used in our illustration passes this test with 92% of users having a good experience and an average score of 32 ms.
  • Cumulative Layout Shift (CLS): measures visual stability. To provide a good user experience, pages should maintain a CLS of less than 0.1. Over 0.25 is considered poor. This score is not measured in seconds but as a fraction of elements that change place unexpectedly during a visit. This site passes this test with 89% of users obtaining a good experience.

If you’re wondering whether a lot of users using slow Internet connections to access your site can have a negative effect on these results, then the answer is yes. Particularly for the Largest Contentful Paint (LCP) score which can be slowed down simply through the speed at which users receive data from your site over their Internet connection.

You can compare your scores to the one above and hopefully your pages pass the assessment. If not, reassure yourself that the majority of sites on Internet may not pass the test. In August 2020, Screaming Frog estimated that only 15% of websites passed the Core Web Vitals assessment.

The site used to illustrate Core Web Vitals results was the home page of amazon.com which should be an illustration of how hard it may be to pass.

Screen shot from https://developers.google.com/speed/pagespeed/insights/
Screen shot from https://developers.google.com/speed/pagespeed/insights/

How big is Core Web Vitals for SEO?

As yet, we have no idea how big a ranking factor passing the Core Web Vitals assessment will be. It is important to remember that it will also be bundled with other signals such as mobile friendliness, safe-browsing, HTTPS-security, and intrusive interstitial guidelines. If you do not use HTTPS on your site, you may get no advantage from passing the Core Web Vitals assessment. Switching from HTTP to HTTPS should be your first priority.

It is very likely that the boost you will get from a good page experience will be a very small one in May 2021. Minor compared to the relevancy of content and links. Getting a visual indicator for good page experience may have a bigger influence in generating traffic than the actual ranking change. However, from May 2021, Core Web Vitals will be part of Google and may well be used by machine learning to tweak results, maybe more so for specific types of searches. So it should not be ignored.

The Core Web Vitals announcement is also important in SEO because it clarified what KPIs will be used to make “page speed” a ranking factor. Google has suggested that they use page speed for ranking since 2008, but it was never clear how they measured this. We now have a score that we can aim to improve.

Is WordPress good for Core Web Vitals?

Using WordPress is not a handicap for passing Core Web Vitals compared to other CMS. However, hosting, themes, image size and other features you add to your site can slow pages down. Writing for SEJ, Roger Montti claims that WordPress Gutenberg 10.1 Boosts Core Web Vitals and this may be an interesting development to follow. Our article 10 tips to boost your site speed also remains relevant today if you are looking for ways to increase page speed and performance.

We’ll conclude by saying that while passing the Core Web Vitals assessment is a great, any improvement to user experience on your site, including page speed, is a good thing to do. And like Google, you can use Core Web Vitals as a tool to measure your progress in improving user experience.

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