Core Web Vitals is a Measurable Ranking Factor

Google’s Page Experience Update, that started its rollout in June, is now complete. After two and a half months the effects are now visible in the search results. In this blog post we analyse the data and show you what happened in the Google SERPs.

If you only have a few minutes, here are the most important points from the blog post in the summary:

  • Page Experience Update complete: Since just a few days, web page performance has been a true ranking factor. (Google’s statement.)
  • Good pages rank slightly better: Based on the Visibility Index, we saw that pages that meet all of Google’s requirements rank one percentage point better than the average.
  • Slow pages rank significantly worse: On the other hand, websites that fail at least one of the Google requirements rank 3.7 percentage points worse.
  • Page experience is a measurable ranking factor: The Core Web Vitals do not replace more important ranking factors such as content, search intent or links, but they are now a measurable, and therefore relevant ranking factor.

If you want to see the detail, read-on for the full blog post with all the data, background and analyses:

Since Google announced, around a year ago, that website performance would become a ranking factor, the priorities of development teams have changed, and agencies have discovered a new source of income.

Under the banner of Page Experience, Google now combines various factors with which the usability of a website can be measured. Alongside the use of HTTPS, mobile device optimisation and avoiding the use of interstitials, the Core Web Vitals have a high priority.

With the Core Web Vitals, Google measures the performance of a website based on three values. These include loading time (Largest Contentful Paint, LCP), reaction speed (First Input Delay, FID) and visual stability of the page (Cumulative Layout Shift, CLS).

Just one of many updates this summer

This summer there were more Google updates than ever before, some of them running in parallel. This makes it difficult to precisely link the cause and effect of individual updates. Was it the Page Experience Update, the Core Update or the Link Spam Update that made the changes?

Because of the multiple updates, the first task is to establish a baseline for the comparisons. To do this, we took the Visibility Index of all domains that had a visibility index of at least 0.1 points at the start of the update, and for which we had data on the Core Web Vitals and indexed them it to a baseline of 100:

Domain visibility development during the Page Speed Update

We then updated the visibility values daily and recorded the change across all domains examined.

As you can see, the visibility of all monitored domains has developed positively on average over the period of the update. The average domain has a 2.7% higher Visibility Index at the end of the update, compared to the start of the update.

The reason for this is that a few large domains lost disproportionately in visibility during the period of the update. This visibility was then distributed over many, smaller domains, so that in total most domains gained visibility.

Above-average success – Domains with good core web vitals

Since we have now established a good baseline for the development of all domains in this period, the next step is the actual comparison:

In a second line in the graph, the following diagram shows the average development of domains that meet all three Google Core Web Vitals.

Domain visibility development during the Page Speed Update

Even if the difference is not dramatic, you can clearly see that domains that meet all values of the Core Web Vitals rank increasingly better than the comparison with all domains in the course of the update.

While the course of these two lines was almost congruent in the first few weeks, visible differences can now be seen at the end of the update.

Expressed in numbers, this means that while all domains have 2.7 percent more visibility at the end of the update than at the start, domains that meet all the requirements of the Core Web Vitals have a full 3.7 percent increase. This one percentage point more growth equates to a 37% difference.

Measurably less visibility: Domains with poor core web vitals

In the next step we come to the cross-check: if domains that meet Google’s Core Web Vitals rank better than the average, domains with poor values must also rank worse.

We have therefore added another line in the following diagram. This shows the Visibility Index of all domains that do not meet at least one of the three Core Web Vitals values, as already seen for the other two lines:

Domain visibility development during the Page Speed Update

Here the deviation from the average is even more pronounced. Domains that do not meet at least one of the Core Web Vitals values have generally ranked a good deal worse than the comparison domains since the update.

Compared to all domains, these domains have 2.7 percentage points less Google visibility since the update. If you compare them with domains that fully meet all core web vitals, there is even a 3.7 percentage point difference.

Slow domains rank 3.7 percentage points worse than fast domains on average.

Due to the redistribution of visibility from a few large to many small domains (without any reference to this update), an interesting coincidence occurs:

Domains that do not meet Google’s Core Web Vitals requirements are no worse at the end of the update than at the beginning. The indexed visibility index of these domains is exactly 100 both at the start and at the end.

One more point needs to be addressed: Correlation does not mean causality. So it can (theoretically) be the case that these shifts can also be traced back to other causes.

Maybe websites that have good Core Web Vitals scores also generally have better content? There is therefore no final evidence, but there are strong indications due to the timing and the announcement by Google.

Conclusion: Core Web Vitals are a measurable and relevant ranking factor

After two and a half months of rollout and a slow start, it is now clear: the page experience in the form of the Core Web Vitals has a measurable influence on the Google rankings. They are therefore a ranking factor and consequently relevant for search engine optimization.

Whether the 3.7 percentage points difference we measured in visibility between fast and slow websites is sufficient to devote time, money and attention to this ranking factor depends on the individual circumstances.

My assessment is that, for most commercial websites, it is worth it. In addition, fast websites not only help the Google ranking, but also improve the user experience across the board.

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