Core Web Vitals

Earlier this month, Google introduced us to the core web vitals. Currently consisting of three metrics, Core Web Vitals are to provide a unified signal in delivering a great user experience. The idea is that they will, in time, benchmark how a page performs in terms of the user experience.

Dimensions such as load time, interactivity and the stability of content as it loads are measured and, by 2021, will also be used as a ranking factor.

The first three core web vitals

At the moment there are only three core web vitals metrics which are as follows:

Largest Contentful Paint (LCP) - (measures loading speed)
First Input Delay (FID) - (measures interactivity) FID of less than 100 milliseconds.
Cumulative Layout Shift (CLS) - (measures stability)

Lets have a look at each of these core web vitals in detail:

Largest Contentful Paint (LCP)

This metric measures the loading performance of your web page. The clear guideline is that the largest contentful paint (LCP) should occur withing 2.5 seconds of when the page first starts loading.

The LCP metric measures "perceived load speed" as it marks the point in the page load timeline when the page's main content has likely loaded. Consequently, a fast LCP helps reassure the user that the page is useful.

Measuring the largest contentful paint of your site is possible using one of the following tools:

First Input Delay (FID)

This metric measures interactivity. To provide a good user experience, pages should have a FID of less than 100 milliseconds. The first input delay measures load responsiveness because it works out the experience that users feel when they are trying to interact with an unresponsive web page. A low FID helps ensure that the page is usable.

The FID measures the time from when a user first interacts with a page to the time when the browser is actually able to respond to that interaction.

As the First Input Delay requires a real user, it cannot be measured in the lab. However, the Total Blocking Time (TBT) metric is lab-measurable, correlates well with FID in the field, and also captures issues that affect interactivity. Optimizations that improve TBT in the lab should also improve FID for your users.

Tools that measure the Total Blocking Time are as follows:

Cumulative Layout Shift (CLS)

There is nothing worse than you're web page moving around when you're trying to read it. This core web vital measures visual stability and measures the amount of unexpected layout shift of visible page content. An ideal measurement is less than 0.1.

This is an important, user-centric metric for measuring visual stability because it helps quantify how often users experience unexpected layout shifts. A low CLS score helps ensure that the page's layout doesn't shift.

The Cummulative Layout Shift of your web page can be measured using one of the following tools:

The Core Web Vitals are being introduced by Google as a unified signal in delivering a great user experience. They serve as means of providing quantifiable metrics to benchmark how well a given web page performs in terms of user experience.

To make things a bit easier, you can contact me to learn more about how to best optimise your website using our SEO Services.

This article was written by Gaz Hall, a UK based SEO Consultant on 30th June 2020.

Gaz has 20 years experience working on SEO projects large and small, locally and globally across a range of sectors.

If you need any SEO advice or would like him to look at your next project then get in touch to arrange a free consultation.