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What are Core Web Vitals?

In Google’s words, Core Web Vitals represent:

A set of real-world, user-centered metrics that quantify key aspects of the user experience. They measure dimensions of web usability such as load time, interactivity, and the stability of content as it loads.

Or, to put it more concretely, Core Web Vitals are how Google quantifies and scores a particular web page’s user experience, which is why the incorporation of CWV into Google’s ranking factors is known as the Page Experience Update.

So what exactly are the factors?

Google uses 3 metrics as their Core Web Vitals to gauge how good a page’s user experience is:


How long does it take for my site to load up?

  • Largest Contentful Paint (LCP): The amount of time to render the largest content element visible in the viewport, from when the user requests the URL. In other words, how long does it take for the user to see the most important content on your page? Note that this isn’t the same as page load time, which measures the amount of time it takes your server to send the first bit of data after someone clicks on your website.

How long until I can use the site?

  • First Input Delay (FID): The time from when a user first interacts with your page (when they clicked a link, tapped on a button, and so on) to the time when the browser responds to that interaction. Basically, how long does it take your site to respond after someone clicks a button or link?

How comfortable am I using this website?

  • Cumulative Layout Shift (CLS): The amount that the page layout shifts during the loading phase. Does the content on your page (text, images, video, links, etc.) move around a lot as it loads? Do buttons, ads or videos load as you scroll, bumping the main content down the page?

Why You Should Care About Core Web Vitals

Putting it bluntly, Core Web Vitals matter because Google is going to start using them as a ranking factor after the Page Experience update.

So why is Google using Core Web Vitals as part of the Page Experience Update?

When looked at together, these 3 metrics give you (and Google) an idea of how delightful or frustrating it is for an actual human to use your pages. And Google’s end goal is to provide people with the best possible experience when they search for something online.

And that includes the experience they have on the pages that Google recommends in its search results.

Core Web Vitals: How Did We Get Here

With the news that Google will be using Core Web Vitals as a ranking factor, you’re likely thinking "why are they doing this? What’s the point?"

To understand why Core Web Vitals matter so much to Google (and, therefore, you), you should understand Google’s ultimate goal: provide people with the best possible experience when searching for things online, whether it’s a product, a piece of content or some information.

It starts, obviously with recommending the best and most relevant content that answers the user’s question.

However, it doesn’t end with just how well Google is able to find relevant content. They want to make sure the pages and websites they recommend are also giving Google’s users the best possible experience.

You should look at the Page Experience Update, therefore, as the next step in Google’s continuing evolution in giving its users the overall best (in Google’s opinion at least) online experience.

In this section, we’ll get into the details of how Google’s search algorithm has changed and evolved to improve people’s online experience.

Early updates: fighting spam tactics

As Google took over the online search market, website owners and marketers at the same time began to look for ways they could manipulate Google’s algorithm to quickly and easily drive traffic to their sites. They used a lot of SEO techniques and strategies(known as "black hat" SEO) that worked but violated Google’s webmaster guidelines.

The result was content appearing high in search results that was of low quality and not completely relevant to the searcher’s query. Essentially, Google had a spam problem.

In order to fight this spam and improve the experience people had with Google’s search engine, they’ve released three major updates known as "Panda" and “Penguin”.

  • Google’s Panda update targeted websites that published extremely thin, over-optimized (stuffed with irrelevant keywords), plagiarized and otherwise low quality content.
  • The Penguin update (which has since been incorporated into Google’s core algorithm) was designed to deal with websites that had acquired illegitimate backlinks in order to rank in search results.

There had been other spam-fighting updates both before and after Panda and Penguin, but these two represent the early major steps in Google’s path toward providing the best possible experience for searchers.

In these cases, those steps were about reducing the amount of spammy sites that it recommended in search results.

Read our full breakdown of Panda and Penguin for the full details on what these two updates were all about.

Moving toward better, more relevant and trustworthy answers

For the past half decade or so, Google’s updates have further pushed them down the path of prioritizing their users’ overall experience with their search engine. Instead of seeking to punish websites that use black hat SEO and other web spam, they have instead sought to promote and highlight more relevant and higher quality content.

This may sound like it’s not much of a difference, but it’s actually a pretty important distinction because it determines how you should go about building your website, creating your content and promoting yourself online.

We can group some updates into what we call "answer engine updates", meaning they dealt with Google’s ability to understand and answer their users’ specific questions:

Google updates timeline from 2013 to 2021
  • Hummingbird: This was, at the time of release in 2013, one of Google’s most significant updates. According to Google, it essentially overhauled its entire search algorithm that allowed it to better understand a user’s entire search query (instead of relying on specific keywords) and the search intent behind that query. The result of the Hummingbird update was that Google could now provide more precise and relevant answers to people’s questions.
  • RankBrain: Technically part of the Hummingbird algorithm, RankBrain is a machine learning AI system that interprets the full context of what topic a keyword is all about. In a very basic sense, it helps Google understand if a search about "apple" is looking for information on fruit or smartphones.
  • Fred: Jokingly named by Googler Gary Illyes on Twitter, the Fred update was released by Google to push down websites that had lower quality content and/or intrusive monetization. Fred wasn’t seeking to promote any specific good thing or penalize a particular black hat tactic, but instead looked to promote websites that gave their users good content without disrupting their browsing experience with obnoxious ads.
  • BERT: Described by Google as "the biggest leap forward in the past five years, and one of the biggest leaps forward in the history of Search," BERT works alongside the RankBrain algorithm to better understand user search intent. It allows Google to better understand the meaning of a word within the context of the entire search query.

"Delighting" web users

Finally, we can also talk about a group of Google updates that seek to promote pages that, in their words, "delight" the people who use them. In this context, “delight” refers to people finding a page fast, simple and easy to use.

Then moving on to the "answer engine"/relevance/quality updates:

  • HTTPS update: Google started using a page’s security in 2014, giving a slight ranking boost to pages that had HTTPS in their URLs. Websites that use HTTPS URLs are more secure and offer website users better protection for their devices and information.
  • Page Speed update: The mobile page speed (the amount of time it takes for mobile users to start loading a page) became a ranking factor in 2018. Simply put, a page that takes less time to load will receive a slight boost over a page that’s slower. Of course, that assumes all other things (content relevance, backlinks, EAT, etc.) being equal.
  • Chrome security warnings: This isn’t a search algorithm update, but is actually a change Google made to its Chrome browser in 2018, marking all non-HTTPS addresses as "not secure" when it displayed the URL in the browser.

There have also been numerous "broad core algorithm updates" along the way. These updates, according to Google, are focused on making sure search results are recommending the best websites and content to searchers.

head icon with a heart insight and the User Experience initials

Core Web Vitals is About the User Experience

We’ve only touched on the major Google updates in this piece, focusing on these changes as examples of Google’s ongoing priority of providing the best possible online experience for their (and, ultimately, your) users. Whether they’re doing that by fighting spam, better interpreting search intent and relevance, or more technical aspects of UX, the goal is the same.

Core Web Vitals, and the Page Experience Update, are really just the next step toward that goal. In fact, since Core Web Vitals are based on real-world user expectations and frustrations, you should see their introduction as an opportunity to quantify the "delightfulness" of your site.

The WooRank Assistant helps identify issues on a page-by-page basis and has recently been updated to include the three CWV checks, helping you to ensure your users have a great on-page experience.

Resources to get started