[Official from Google] Core Web Vitals will become an essential ranking factor in June 2021

Official announcement from Google

On the official Twitter page of Google Search - Google Search Central made an announcement and immediately this information captured the attention of many people:

In the upcoming May 2021**, the Core Web Vitals index will become an essential website ranking factor, alongside the existing User Experience (UX) factors.
Official announcement from Google
Official announcement from Google

**Update: Core Web Vital was originally planned by Google to be updated in May 2021, but there have been some changes and updates announced that it will gradually leave the update in June 2021.

2. What are Core Web Vitals?

For those of you who do SEO and often need to check the website indexes on Google Search Console, in recent times, you must have realized a "strange" change of Google.

It's that the Speed Report section in the Google Search Console page has disappeared, replaced by an item called Core Web Vitals report.

So what is Core Web Vitals and why was it chosen to become a Google ranking factor in the future?

In a nutshell, Core Web Vitals is a collection of essential website metrics covering aspects related to the user experience on the page.

Core Web Vitals are metrics measured by Chrome UX Report and Google Search Console to evaluate website performance and rank SEO scores. Each metric represents an aspect of user experience, corresponding to the following ranking factors:

  • Loading: Page loading speed
  • Interactivity: Interoperability
  • Visual stability: Stability when displaying
Core Web Vitals
Core Web Vitals

Based on the following 3 corresponding indicators forming Core Web Vitals, they are:

  • LCP (Largest Contentful Paint)
LCP measures Time to complete the main content that is first displayed when the page has finished loading. The ideal LCP should be 2.5 seconds or faster.

  • FID (First Input Delay)
The time the user responds to the first interaction on the website. The FID index needs to be optimized to get under 100 milliseconds.

  • CLS (Cumulate Layout Shift)
Layout change score in cumulative form. Or it can be understood that this is an indicator of the volume of image layouts that are suddenly shifted on the website. The best CLS that each website needs to achieve for the best experience is less than 0.1.


Core Web Vitals 3 stats
Core Web Vitals 3 stats

According to Google, these measurement signals help improve the user experience and interactivity on the website better and better.

And accordingly, any changes of Core Web Vitals will be related to best meeting the user's desire for the experience on the website.

Core Web Vitals and the Page Experience algorithm

In the latest update at the end of May 2020, Google announced that Page Expericence will become a new ranking factor and will be officially applied in 2021.

In addition, Google also said that this new Page Expericence algorithm will be a ranking factor for Top Stories on mobile devices, and that the preference for AMP will be gone.

And closest to the appearance of the Core Web Vitals metric, the Page Expericence algorithm will include the (new) Core Web Vitals metrics along with previously applied user experience signals. More specifically with the following 5 measurement signals:

  • Core web vitals: LCP, FID, CLP
  • Mobile friendly: Friendly to mobile devices
  • Safe browsing: Surf the web safely
  • HTTPS: Secure https
  • Mobile popup algorithm/No intrusive interstitials: Rules for interstitial ads (appearance of popups, ...)
One more important piece of information from the big Google is that they may add an index label showing the Page Expericence quality of websites on search results in 2021.

However, there are actually quite a few websites that do not qualify for this label. Because according to a latest study, only about 15% of websites are eligible to pass Google's Core Web Vitals index test.

Core Web Vitals Stats Checker Tools

You can view the Core Web Vital metrics report for your website at the link https://web.dev/ or with one of these 6 tools: PageSpeed Insights, Chrome DevTools, Lighthouse, Google Search Console, Chrome UX Report or Web Vitals Extension.

Core Web Vitals Stats Checker Tools
Core Web Vitals Stats Checker Tools

Based on the table above, we can see some performance differences between tools when checking Website Essentials. Some tools use field data from real user experiences, others are based on performance simulation of user behavior in the lab.

Where FID metrics are replaced by TBT – Total Blocking Time (total blocking time for user input feedback) are metrics measured against simulated lab data.

According to the big Google, tools using field data will be a better choice and they will be used as a ranking signal for your website.

However, one thing that is quite remarkable when using field data to measure Page Expericence is this: Optimization score will be influenced by actual users. For example, if users use weaker networks or devices to view your website, the UX experience score on the page will also be underestimated compared to a competitor's website with similar optimization scores. your device, but accessed by a device with better connection conditions.

A quick review of Core Web Vitals metrics tools on:
  • Google Search Console: Provides an overview of the Site Essentials Indicators management report
  • Chrome DevTools & Lighthouse: Help webmasters dig deeper and perform optimizations in practice.
  • Chrome UX Report & Web Vitals Extension: A quick assessment of the effectiveness of the experience on the website.

How important are Core Web Vitals for SEOs?

One thing's for sure, any update or change in Google's ranking signals has the power to impact search rankings and SEOs should start optimizing it now.

Google announced that the signal about the on-page experience will become the deciding factor, in cases where websites have similar ratings for content quality.

Therefore, in addition to producing useful content with the right customer intent, SEOs need to focus their resources on optimizing the experience (Page Expericence & Core Web Vitals) and Page Authority authority) of the page before they are applied and become key ranking factors.


As such, there are algorithm changes as well as Google's latest announcements about the ranking factors that will be focused in 2021: Core Web Vitals & Page Experience. This is a signal for a long-distance race for webmasters, who need to optimize the user experience on the page in addition to producing useful content. At the same time, website design trends have also changed quite a bit to meet these new Google ranking signals.

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