Google Core Web Vitals: What You Need To Know

Google Core Web Vitals: What You Need To Know

This post takes a look at the upcoming Google Core Web Vitals Update. Here we will look at the background to this update, the core web vitals report, page experience signals, core web vitals themselves, how to assess other areas of page experience and the potential impact this update.

Read the article below. TLDR – skip to the Potential Impact.

Is This Update A Speed Update?

This update is focused mainly around speed. In fact, the Web Vitals that Google is looking for (LCP, FID and CLS) are all measured against speed.

It is clear that Google is going in pretty hard with the notion that user experience = fast websites.

I’ve recently spoken to developers and designers really excited about the interactivity factor of this update.

“Does this mean Google is going to love sites with loads of interactions and animations and fancy buttons that flip round when we hover over them?”


Interactivity, measured by First Input Delay, is the time it takes for the browser to respond to interactions.

Core Web Vitals

So what exactly are core web vitals?

Core web vitals are metrics the Google will be used to measure page experience. The core web vitals are:

  • Largest Contentful Paint (LCP) – Loading
  • First Input Delay (FID) – Interactivity
  • Cumulative Layout Shift (CLS) – Visual Stability

Below we break down these metrics, discussing what they are and how site owners can optimise for them.

LCP – Loading

Loading is measured within the Core Web Vitals Report by Largest Contentful Paint (LCP).

Google has been shifting from Time to First Byte (TTFB) to LCP as they realise that server response time is a poor indication of how real content loads for real users.

LCP measures how fast visible content loads for users.

Google ‘s own definition of LCP is as follows:

“LCP is an important, user-centric metric for measuring perceived load speed because it marks the point in the page load timeline when the page’s main content has likely loaded—a fast LCP helps reassure the user that the page is useful.”

In a nutshell: LCP is giving you a more accurate reading on how fast real users can load real content. Much more accurate that looking at the time it takes for a browser to start sending information to a browser.

How can site owners improve LCP?

Site owners can fix poor LCP issues by improving the following:

  • Server response times
  • Render-blocking JavaScript and CSS
  • Resource load times
  • Client-side rendering

FID – Interactivity

Interactivity is measured to some extent within the Core Web Vitals Report by First Input Delay define First Input Delay as follows:

“First Input Delay (FID) measures the time from when a user first interacts with your site (i.e. when they click a link, tap on a button, or use a custom, JavaScript-powered control) to the time when the browser is actually able to respond to that interaction.”

Think of First Input Delay as the delay between actions like clips or taps and the browser response. As a tip, scrolling or zooming doesn’t trigger FID.

How can site owners improve FID?

Site owners can fix poor FID issues by improving the following:

  • JavaScript execution time
  • Breaking up long tasks

Site owners should also consider:

  • Optimising pages for interaction readiness
  • Using a web worker

CLS – Visual Stability

Roger Montti describes Cumulative Layout Shift as:

“…the unexpected shifting of web page elements while the page is still downloading. The kinds of elements that tend to cause shift are fonts, images, videos, contact forms, buttons and other kinds of content.”

Have you ever loaded a website, prepared yourself to devour a nice piece of content, only to be visually assaulted by a sneaky, sneaky ad? Or maybe a header image that hasn’t properly loaded yet?

That is CLS in action.

How can site owners improve CLS?

Site owners looking to reduce FID issues should consider addressing the following:

  • Dimensionless images
  • Dimensionless embeds, iFrames and ads
  • Dynamically injected content
  • FOIT/Fout web fonts
  • Network dependent actions that update DOM

Core Web Vitals Google Search Console Report

The core web vitals report’s aim is to help you fix poor page experiences on your site. This report can be found in Google Search Console under “Enhancements”.

I am a sucker for SEO tools, but they’re always open to interpretation. That’s why I love the data in search console. Seeing areas of your site grouped into good, needing improvement and poor is so valuable when coming straight from Google’s mouth. We have a bit of work to do on the site above…

Other Ways To Measure Core Web Vitals

Webmasters have [as of May 2020], 6 ways to measure Core Web Vitals.

  • Google Search Console
  • PageSpeed Insights
  • Lighthouse
  • Chrome DevTools
  • Chrome UX Report
  • Web Vitals Extension

Personally, I love the Web Vitals Chrome Extension. Probably because it gives me those oh so satisfying green circles when testing this site. Shout out to NitroPack for saving me hours pulling out my hair trying to optimise for Core Web Vitals.

Evaluating Page Experience Signals in 2020

Interested in evaluating your page experience? Play around with some of the tools below.

  • Lighthouse Speed Test
  • Mobile Friendliness Test
  • Google Search Console
  • Chrome UX Report
  • Chrome DevTools

Also, make sure you are following the guidelines on:

  • Safe Browsing
  • Interstitials

Page Experience or User Experience

Core Web Vitals measure page experience. Not user experiencePage experience and user experience are closely linked.

Page experience can be thought of as a component of user experience. If a user has a poor page experience, they are likely to have a poor user experience.

However, if a page demonstrates excellent page experience (i.e it ticks all of Google’s quantifiable metric boxes; CWVs, mobile-friendliness, etc.), but poor user experience; bad searcher intent, non-sensical page hierarchy, confusing navigation, poor structure, etc, then the page could struggle to remain relevant and may struggle with parts of Google’s Rankbrain algorithm.

With this in mind, the Core Web Vitals cannot be dubbed a ‘user experience factor’. Rather, an update focusing on the section of user experience that Google can quantify. Good content is still likely to rank regardless. If a user wants a piece of content, that no-one else has or from a brand they trust, then they will likely stick around and suffer poor page experience. However, in eCommerce and heavy commercial intent searches, where content is more or less standardised to a certain degree, page experience factors will likely become a deciding factor.

Besides the Core Web Vitals, Google will also be including the following factors into this update grouped under the page experience category:

  • Mobile-friendliness
  • Safe Browsing
  • HTTPS-security
  • Intrusive interstitial guidelines

But these page experience factors have been known for years and some of them even have their very own penalty:

So has much changed, or are SEOs and webmasters just getting the rare chance to peek under Google’s hood with the Core Web Vitals report?

Potential Impact

With any Google update, there is always a potential for massive chaos. However, I don’t see massive changes here.

Yes, there will be winners and losers, but the sites not currently ahead of the curve and slow to adapt are always going to get hit whenever the goal-posts are moved.

Personally, I think the early adopters already optimising heavily for speed and CLS will see slight gains here. These are the sites that are ahead of the curve in most updates. Similar to HTTPS, over time most sites will catch on. SEO execs fighting for faster sites that don’t “jump around” while loading will have another argument for prioritising speed fixes. Speed has to some degree, became a sink or swim factor in competitive niches, this update could be the final nail in the coffin for slow websites.

In Google’s own words:

“A good page experience doesn’t override having great, relevant content. However, in cases where there are multiple pages that have similar content, page experience becomes much more important for visibility in Search.”

Talk to us about speed optimisation. We’ve got a few tricks up our sleeves and are “money-back-level” confident we can help you pass all the Core Web Vitals tests.

Further Reading


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