Google Announces Core Web Vitals – User Experience Signals

Core Web Vitals from Google is their initiative to provide guidance on User Experience signals for site owners.

As a website owner or developer, you’ll no doubt be familiar with Google Chrome’s web dev tools: just press f12, open the audit tab and click “generate report”. The Chrome browser then audits your website or app, either the desktop or simulated mobile version. This is Google’s Lighthouse engine, a tool to help you improve the quality of your web pages.

Lighthouse reports mark your performance, accessibility, best practices and SEO. Your marks out of 100 indicate where your site is doing well or where it might need improvement.

Once you dive into the metrics, there are a number of key data points such as First Paint, First Contentful Paint (FCP), First Meaningful Paint (FMP), Time to Interactive (TTI) etc. If you’re technical, these metrics are gold dust. You can pinpoint where in the code of your website you need to make improvements to make your pages perform better.

Performance is crucial to delivering a great user experience.  In recent years, Google has measured the web page elements that help this experience, chiefly page speed and mobile-friendliness.

Web Vitals aims to simplify User Experience audits.

Core Web Vitals.

The Core Web Vitals are three specific metrics that Google will focus on to help website owners to improve UX;

  • Loading.
  • Interactivity.
  • Visual stability.

Remember, Google wants to simplify the auditing of your UX so these are easily understandable metrics. However, just to satisfy the geekiest of you, Google has still managed to give these figures technical names:

Largest Contentful Paint (LCP).

Last Contentful Paint (LCP).

This is a measurement of loading performance. When LCP is fulfilled, this is the likelihood that the web page has fully loaded and is thus useful/useable by a user. Google has set a figure of 2.5 seconds for LCP, beyond which your page needs improvement (2.5 – 4 seconds) or is just poor (4+ seconds).

First Input Delay (FID).

First Input Delay (FID).

FID is a measure of interactivity. Once your user is able to click, scroll and interact with your web page, that’s your FID metric. Unlike LCP, FID needs to be fast. If your users can interact in less than 100 milliseconds, or a tenth of a second, that’s good. 100-300 milliseconds means your page needs improvement, 300+ is a poor experience.

Cumulative Layout Shift (CLS).

Cumulative Layout Shift (CLS).

Have you ever landed on a web page, started to read and then an ad or video has loaded where you were reading and the layout shifts? Frustrating isn’t it. CLS measures this and looks at how much of your screen is affected by layout and how far that shift is once measured. 0.1 is a good experience, 0.1 to 0.25 will require improvements and anything beyond 2.5 is a poor experience.

Google will be “surfacing” these metrics across all its tools including:

  • Chrome User Experience Report which feeds into…
  • PageSpeed Insights.
  • Google Search Console.

These tools will be evolving over time so expect that they wont stay still.

Whatever you do with your website, user experience is so important. Make sure you build, from the ground up, and continue develop your websites to take onboard all these factors, they absolutely must be user-centric.


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