Core Web Vitals – A quick guide for marketing managers

Are you responsible for managing SEO? Have you heard the term ‘Core Web Vitals’ but are not sure to what it refers?

We have prepared this quick guide to get you up to speed with Core Web Vitals and why they are essential for SEO in less than a thousand words.

Let’s start with what Core Web Vitals are.

What are Core Web Vitals?

Core Web Vitals are a set of metrics that measure the user experience of a web page. There are currently three Core Web Vitals that measure web page loading, interactivity, and visual stability.

We will now take a look at the metrics being used to measure Core Web Vitals.

Largest Contentful Paint (LCP)

LCP measures the amount of time taken to load and render the largest image or text block displayed in the viewport.

Google likely chose Largest Contentful Paint to measure page loading for UX as it marks the point at which the main content of a webpage has probably loaded.

An LCP of 2.5 seconds or less is considered acceptable and LCPs of over 4 seconds are considered poor.

To improve LCP, generally, you need to review the following:

  • Slow server response times
  • Render-blocking CSS and Javascript
  • Slow load times of resources
  • Slow client-side rendering

First Input Delay (FID)

FID is the amount of time taken between when a visitor first interacts with a webpage and when the page processes the interaction. In most cases, it is the difference in time between a visitor clicking an element on a webpage and the browser responding to that click.

First Input Delay measures a page’s interactivity and responsiveness.

A good FID score is 100ms or less, and a score above 300ms is considered poor.

To improve your First Input Delay do the following:

  • Lessen the effect of third-party code on page loading and rendering
  • Shorten JavaScript execution time
  • Reduce main thread work
  • Lower request counts and reduce file transfer sizes

Cumulative Layout Shift (CLS)

CLS is a measure of the visual stability of a web page. You calculate Cumulative Layout Shift by summing the scores of layout shifts that occur. You record a layout shift when an element of the web page changes position during page loading and rendering.

A CLS score of less than 0.1 is good, and a score above 0.25 is considered poor.

To improve Cumulative Layout Shift:

  • Ensure image and video elements include height and width attributes
  • Do not add new content above content that has already loaded on the page unless the visitor initiates it
  • Use transform animations rather than animating CSS properties

Google’s Core Web Vitals ranking factor announcement

In May 2020, Google announced that Core Web Vitals would become part of their search algorithm. Google is using Core Web Vitals so that it can better evaluate a web page for user experience.

In June 2021, Google started rolling out Core Web Vitals.

Core Web Vitals testing and reporting

You will want to find out your current LCP, FID and CLS scores to see how the page experience update will impact your website.  You can use the following tools to measure the stated Core Web Vitals metrics:

  • PageSpeed Insights – LCP, FID and CLS
  • Chrome UX Report – LCP, FID and CLS
  • Search Console – LCP, FID and CLS
  • Chrome Dev Tools – LCP and CLS
  • Lighthouse – LCP and CLS
  • Web Vitals Extension – LCP, FID and CLS

You should ensure that Google’s page experience update does not negatively affect your organic search rankings. To do this, you will need to identify LCP, FID and CLS scores that are worse than ‘good’, and determine which page load and rendering factors are causing the low scores.

Once you know what needs improving on your site, you can approach your developers to implement changes to rectify the issues affecting page loading and rendering. If you are on a platform such as WordPress, you may be able to use ready-made plugins that can improve your site’s performance.

Wrapping up

You should now have a much better idea of what Core Web Vitals are and how they could be affecting your organic search rankings.

If you would like to speak with one of our team about our technical SEO services, you can email us

About the author

Daniel Lee

I am a digital marketing strategist with more than eleven years' experience. I have worked in digital marketing agencies, as well as client-side. My clients include small businesses all the way up to organisations with revenue in the billions. I provide marketing consultancy both in the UK and the US. I hold a Master of Science degree in International Marketing, and I am a member of the Chartered Institute of Marketing.

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