core web vitals

Core Web Vitals: How The New Ranking Signals Impact SEO

Jonas Sickler, Digital Marketing Analyst

Key Points

  • Core Web Vitals are three metrics included in Google’s page experience signals that quantify the user experience of interacting with a page.
  • Core Web Vitals measure how quickly a page is visible, how long it takes before a user can interact with the page, and the visual stability of the elements on the page.
  • The metrics that currently make up Core Web Vitals are Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS), though these could change over time.

Google has always been user-centric. From eliminating keyword stuffing to making page load time a ranking factor, to mobile-first ranking, they’ve constantly pushed for a better user experience. Core Web Vitals are yet another push in that direction.

Read on to learn what Core Web Vitals are, why they matter, and how you can improve the associated scores for your web pages.

What are Core Web Vitals?


Core Web Vitals (CWV)

Core Web Vitals (CWV) are a set of quantitative performance metrics Google developed to measure qualitative users experiences on a web page. These metrics specifically measure loading experience (LCP), interactivity (FID), and visual stability (CLS) of web page content.

In May 2020, Google announced that page experience signals would become an organic ranking factor. More specifically, Google’s algorithm would begin to measure the following metrics to calculate user experience:

  • Mobile friendliness
  • Safe browsing
  • Content accessibility via a lack of intrusive interstitials (pop-ups) 

In November 2020, Google added three new metrics to their page experience signals called Core Web Vitals:

  • Largest Contentful Paint (LCP)
  • First Input Delay (FID)
  • Cumulative Layout Shift (CLS)

When did Core Web Vitals roll out?

Core Web Vitals became a Google ranking factor for top stories on Thursday June 17 2021, and they’ll be fully rolled out as part of a page experience update by the end of August 2021. However, Google has stated that they will update page experience signals each year. So, expect these to evolve over time. 

Why Core Web Vitals are important 

CWV help web developers provide a great user experience. As a result, users are more satisfied, more likely to return, and more likely to recommend your website to others. Conversely, if pages are slow, unstable, or cluttered with popups, users will hesitate to return.

Now, think about how that impacts Google’s brand and revenue. If you repeatedly click on links in the SERP that deliver a bad experience, you’ll become frustrated with Google. Eventually, you may try alternative search engines, and that means less advertising revenue for Google.

Google Core Web Vitals are measurable SEO performance metrics that give you a sense of how people experience your website. They provide you with specific, measurable data points to improve the overall user experience on your website. When users have a better experience, they’re more likely to return.

Ultimately, CWV doesn’t just improve your organic rankings, although that’s part of it. It provides your audience with a superior experience. And that translates into more engaged customers, higher conversion rates, and potentially other positive benefits.

It’s also important to note that, although Core Web Vitals are important, Google still seeks to rank pages with the best information overall, even if the page experience is subpar.


Great page experience doesn’t override having great page content. However, in cases where there are many pages that may be similar in relevance, page experience can be much more important for visibility in Search.

The three components of Google’s Core Web Vitals

Now let’s look at each of the 3 Core Web Vitals components, including thresholds and target ranges.

core web vitals LCP (largest contentful paint) score range
core web vitals FID (first input delay) score range
core web vitals CLS (cumulative layout shift) score range

LCP: Largest Contentful Paint


Largest Contentful Paint (LCP)

LCP is a Core Web Vitals metric that measures loading time. More specifically, it measures the amount of time it takes to render the largest content element within the viewable area of a user’s screen. It does not measure the entire page.

Depending on the page, this element could be:

  • Featured image
  • H1
  • Blocks of text
  • <img> element
  • <image> element inside an <svg> element
  • Image inside a <video> element
  • Background image loaded with the url() function

Google considers an LCP of 2.5 seconds or less to be a “good” URL (segmented by mobile and desktop). A score between 2.5 seconds and four seconds needs improvement. And, a score higher than four seconds is considered poor.

How can you improve LCP scores? Start by reviewing Google’s LCP optimization overview.

Ways to improve your LCP score

  • Remove any unnecessarily third-party scripts
  • Upgrade to a faster web host
  • Install a CDN
  • Cache assets
  • Set up lazy loading of images
  • Remove large page elements that take more time to load (large images, GIFs, etc.)
  • Minify your CSS
  • Follow Google’s advice for your specific URL (See how to measure Core Web Vitals below.)

Two other related metrics to consider when diagnosing page speed issues are First Contentful Paint (FCP), and Time to First Byte (TTFB).

FID: First Input Delay


First Input Delay (FID)

FID is a Core Web Vitals metric that measures time to interactive. Specifically, it measures the time between the first user input with a web page (clicking, tapping, swiping, etc.) and when that page responds.

Think of interactivity as page responsiveness. The longer the delay, the more likely a user will be frustrated since the page seems unresponsive.

What is a good FID score?

Google considers an FID of 100 milliseconds or less to be “good”. A page needs to hit this mark 75% of the time from collected field data on both mobile and desktop.

Where should you begin? Start by reviewing Google’s FID optimization overview

Ways to improve your FID score

  • Minimize (or defer) JavaScript since it’s difficult, if not impossible, for users to interact with your site when JS is running
  • Remove non-essential third-party scripts that have to load before a user can interact with your site (heat maps, analytics, etc.)
  • Implement browser caching, which stores certain elements in a user’s browser so that they don’t have to be reloaded every time
  • Follow Google’s advice for your specific URL (See how to measure Core Web Vitals below.)

CLS: Cumulative Layout Shift


Cumulative Layout Shift (CLS)

CLS is a Core Web Vitals metric that measures the visual stability of a page. It looks at the proportion of the screen that shifts, and how far elements move.

Few things are more frustrating than trying to interact with page elements that jump around unexpectedly. Unexpected layout shifts are especially problematic when they have real-world consequences like accidentally ordering something, or clicking on an ad that takes you to another website.

As a site owner or developer, it’s important to calculate your CLS based on real user interactions, and not just lab data. For example, ads may not load on your staging site, so your scores won’t reflect real-world experiences.

CLS is calculated by multiplying the impact fraction (percentage of viewport that shifts) by the distance fraction (movement distance divided by the viewport height).

A burst of layout shifts is when multiple shifts rapidly occur over a period of five seconds or less, with less than a second between each shift. CLS measures the largest burst of layout shifts that occurs over the lifespan of a page. For detailed information on how this is calculated, read Google’s documentation here.

Google considers a CLS score of 0.1 or less to be good, and a page needs to hit this mark 75% of the time on both mobile and desktop.

Where should you begin? Start by reviewing Google’s CLS optimization overview

Ways to improve your CLS score

  • Use set size attribute dimensions for any media (images, GIFs, etc) so that the user’s browser knows how much space they’ll take up and won’t suddenly change the dimensions
  • Put all ads in reserved spaces so that they don’t appear suddenly, causing content to shift
  • Avoid pop-ups or banners that cause the screen layout to shift when the site is first loading
  • Follow Google’s advice for your specific URL (See how to measure Core Web Vitals below.)
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Tools to measure Core Web Vitals

There are a number of tools you can use to measure Core Web Vitals scores on your site to compare its performance against the recommended benchmarks.

Google tools

One of the easiest ways is the Core Web Vitals report (within the Experience tab) in Google Search Console. It will tell you which URLs are “good” (fast loading), which need improvement, and which score poorly, across both mobile and desktop devices. Just be aware that the data is a bit delayed.

If you click on a specific URL, and then click “PageSpeed Insights“, you’ll see specific recommendations for how to improve the over page experience. (Or, you can simply go to Google PageSpeed Insights directly.) Some of the recommendations will be relatively simple, like optimizing image size to reduce load time. Others will be more complex, requiring you to dig into your site’s code to reduce unused JavaScript or eliminate render blocking resources.

Google Lighthouse is a page performance measurement tool that’s perhaps most useful to web developers, and it includes audits that Google PageSpeed Insights doesn’t have.

Google Web.Dev allows you to enter any URL on your site and get recommendations for improving Core Web Vitals, as well as general best practices recommendations for improving the overall user experience.

From Google Chrome 88 and higher, you can now see Core Web Vitals data in the Chrome DevTools performance panel. From Chrome 90, there’s an overlay tool.

You can also use the Chrome User Experience Report (CrUX).

Core web vitals Chrome extension

If you’re looking for a Google Chrome extension, the Web Vitals extension is a quick and easy way to see whether any page meets the Core Web Vitals benchmarks provided by Google. Just be aware that the extension is not a tool developed by Google itself.


Depending on your CMS, you may have other options, as well. For example, if your site is built on WordPress, there are third-party plugins that can help improve Core Web Vitals performance, such as WP Rocket, NitroPack, or Asset Clean Up.


You can measure any page’s CWV scores directly from your Chrome browser using Google’s Lighthouse DevTool. Simply inspect the page and click the Lighthouse tab.

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How will Google’s Core Web Vitals impact your SEO?

The Core Web Vitals SEO impact will be severe for some websites with poor page experience. However, most websites with good user experience won’t see any impact at all. That’s because Google still prioritizes other search ranking signals that matter more, like the quality of the content on a page.

So in terms of search engine optimization (SEO) priorities, focus first and foremost on creating high quality content that aligns with search intent and thoroughly covers the topic. Once you’ve done that, focus on optimizing pages for Core Web Vitals metrics for an even greater organic lift.

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