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A Marketer’s Guide to Core Web Vitals

17 May 2021 Eva Mullineaux

in SEO, Trending

You may have seen the Core Web Vitals dashboard in your Google Search Console or heard rumblings of a Google ranking factor update coming this year, but what are Core Web Vitals and how do they impact your business? Core Web Vitals are Google’s way of quantifying user experience and will roll out as a ranking factor between mid-June and August 2021. As Core Web Vitals will impact website rank, brands need to understand and prioritize this SEO development, so that they continue to win in search results and are easily discovered by consumers online.



Core Web Vitals refers to a set of metrics that Google is using to measure UX more accurately. These metrics relate to load time, interactivity of a page, and the visual stability of content as it loads. These scores are calculated on a page-by-page basis on both desktop and mobile; if websites perform well, site visibility can increase.



Google’s aim is to make sure that all the websites included in their index are offering the best experience for their searchers. By making Core Web Vitals a ranking factor, Google is leveraging search visibility to encourage website owners and developers to focus on UX. If a site and its competitor both rank for an important keyword—but one has better UX than the other—Google will reward that site with better position on their search results page for that keyword.

What does it mean to not pass the Core Web Vitals assessment?

If your site does not have a passing score on the different Core Web Vitals metrics, this can impact rankings and signifies that your website has poor user experience. Having strong UX is critical for ecommerce sites in particular; those that take a long time to load, have slow-acting CTA buttons, or page content that jumps around are problematic now and repercussions will increase with the Core Web Vitals rollout. Having a strong user experience, and, therefore, passing the Core Web Vitals assessment can help increase conversion rates.

What are the different Core Web Vitals metrics?

The metrics that make up Core Web Vitals include Largest Contentful Paint, First Input Delay, and Cumulative Layout Shift.

What is Largest Contentful Paint, or LCP?

Largest Contentful Paint, or LCP, refers to loading speed. LCP measures how long it takes for all of the content above the fold on a page to load. LCP can be affected by slow server response times or client-side rendering.

For example, if you open a news article and the cover photo is the first thing you see on the screen, LCP measures how long it takes for that entire image to fully load on the page.

What is First Input Delay, or FID?

First Input Delay, or FID, refers to interactivity. FID measures how long it takes for your browser to begin executing an action once a user first tries to initiate an event, such as clicking on a button. FID can be affected by your browser trying to execute too many actions or load too many things at the same time, such as large JS files.

For example, if a user clicks on a button on your site to open a pop-up contact form, FID measures how long it takes for the browser to begin initiating that pop-up.

What is Cumulative Layout Shift, or CLS?

Cumulative Layout Shift, or CLS, refers to visual stability. It measures how often and by how much elements on a page unexpectedly move. CLS can be affected by images and videos of unspecified dimensions rendering, fonts that render larger or smaller than its fallback, or third-party widgets that resize themselves dynamically.

This can be especially frustrating for users on mobile because a user could be trying to click on a button and before they can click on it, the content on the page has shifted because of something large rendering higher up on the page and the button gets pushed farther down the page, maybe even off the screen. They then must scroll further down the page to find the button they were trying to click in the first place.



Now that we know what the Core Web Vitals metrics are, why should you care about them?

Google has been indicating that UX is important for a while now. Google has already been using the following Page Experience metrics as ranking signals:

Core Web Vitals and User Experience

Core Web Vitals is just a logical extension of these other Page Experience metrics. Google wants to ensure that searchers are landing on pages that give them exactly what they are looking for in a way that is intuitive and creates a pleasant experience on the site.

With Core Web Vitals, Google is enticing website owners and developers to follow the best practices of UX in their website creation to create user friendly websites by leveraging rankings. Meeting the standards of Core Web Vitals across the different metrics could be a tie-breaking ranking factor and the difference between ranking for an important keyword and a competitor taking your brand’s place.

Is Core Web Vitals important for Bing, Yahoo, and other search engines too?

Google had 92.41% of all searches in 2020. The other major search engines generally follow suit with Google, so it is likely that the other search engines will begin rolling out their own ranking factors like Core Web Vitals.



Here are some of the best tools to check Core Web Vitals for your site:

    • Core Web Vitals Dashboard in Google Search Console
    • PageSpeed Insights
    • Lighthouse for Developers
    • Chrome DevTools, which you can find by going to the right-hand corner of your Chrome browser, hovering over More Tools, and selecting Developer Tools.
    • Web Vitals Chrome extension
    • Experte Core Web Vitals Check
    • CrUX Dashboard Creator from Github


It can be a little difficult to understand what the different Core Web Vitals are referring to and what the scores mean. As mentioned prior, Core Web Vitals are a tie-breaking ranking factor: you want your scores on the Core Web Vitals metrics to be better than those of your competitors. While top scores across the board are ideal, it is most important to have stronger scores than your competitors so that you have a better chance of ranking against them.

Core Web Vitals also use field data to collect real-life data points over the last 28 days and give an accurate measure of each metric included in Core Web Vitals. To receive a passing “Good” evaluation on a metric of Core Web Vitals, 75% of visits to your site must be within the “Good” range for a given metric. Meaning: if 75% of visits to your site experience a LCP of 5 seconds, then the score for that page will be based off that 5 seconds and will be given a “Poor” evaluation for LCP. Using this 75th percentile, a 28-day window, and field data gives a more accurate view of how a site is performing against these metrics.

Having “Good” scores across all three Core Web Vitals metrics counts as passing the Core Web Vitals assessment. This means that your page delivers a positive page experience and, with the roll out of Core Web Vitals as a ranking factor, your page will be rewarded for having fast loading times, interactivity, and strong visual stability.

SEMRush found that up to 84% of URLs ranking in the top 10 on mobile had Core Web Vitals that were scoring as “Poor” or “Needs Improvement.” They also found that “The better all three [Core Web Vitals] metrics are, the higher the position [of a URL with “Good” vital ratings] on SERPs.” Having strong Core Web Vitals metrics leads Google to reward your page with better rankings. However, not everyone is ready for the roll out of Core Web Vitals in the coming months.



Once you know where your brand’s website stands with Core Web Vitals, it can be hard to know how to fix these issues and even where to start. Oftentimes, developers are most helpful in actioning fixes.

Tips for Improving LCP

Ensure that all images are compressed and are served in next generation format, meaning that the image files are around 100 KB or less and do not require a lot of effort to fully load. Scaling images and defining their size can also help improve issues with LCP, ensuring that images are loading only as large or small as desired.

Tips for Improving FID

To improve FID, consider delivering smaller JavaScript payloads so as not to force browsers to execute too many large tasks at once. Additionally, minimizing render blocking JavaScript can help with FID issues. Minimizing unnecessary JavaScript and CSS, oftentimes leftover from the theme that was used to build the site or from third-party widgets or plugins that are now unused, helps to improve FID.

Tips for Improving CLS

Scaling images properly and defining their sizes helps to fight CLS. When the dimensions of images are undefined, the browser loading them is unsure what size they should be—so they might be rendered far larger or smaller than intended and could be loading faster than above-fold content. Avoid any occurrences of CLS by ensuring that no content loads above already loaded content unless actioned by the user.



At Stella Rising, our award-winning SEO team can offer insights into Core Web Vitals, ensuring that your brand stays ahead of the curve. Learn more about Core Web Vitals from our technical SEO and UX experts at Stella Rising by connecting with us today.

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