What is This ‘Core Web Vitals’ Thing Everyone is Talking About?

We’ve all watched a movie or series where a nurse begins their care of a critically-injured patient by asking “have you checked their vitals?”

Human vitals are the body’s most basic functions that are routinely monitored by medics to check a person’s health. They are: body temperature, pulse, respiration, and blood pressure.

In much the same way, web vitals perform the same function to a website as vitals work on a human.

Web vitals were created by Google to give a comprehensive, broad view of quality signs that are fundamental to providing a great digital experience for users. 

Over the years Google has built a supply of digital tools that measure site performance as well as provide reports. While many website owners have neglected these tools – given the anxiety-inducing number of those available and complexity of figuring out which are more important than others – others have become experts in using them to tweak and rebuilt online experiences.

But the challenge is real. There is real complexity in understanding algorithms and building fully-optimized experiences with green lights on all metrics. Plus the overwhelming weight of competitors both big and small who are also trying to do exactly that and push you off top spot in search engine results.

Well, Google’s Core Web Vitals is an attempt to squeeze all of this complexity into a more simplified environment so that you can focus on the core metrics that drive the overall performance. 

Core Web Vitals consist of 3 specific page speed measurements and user interaction measurements:

1. Largest contentful paint (LCP)
2. First input delay (FID)
3. Cumulative layout shift (CLS)

There are a bunch of other web vitals that when taken together have important functions in deciding how good a particular page performs. These include mobile friendliness, HTTPS, safe browsing, structure, and total blocking time.

Largest contentful paint measures the loading performance. Ideally, the time of your largest contentful paint should be within 2.5 seconds to give a good user experience.

LCP is the time it takes between clicking a link and seeing the majority of the content on the screen. It’s more targeted to the user experience because there are other page speed metrics like first contextual paint and TTFB that don’t actually analyze exactly what a user of the site experiences.

LCP is extremely useful when deciding whether to remove particular images and videos for a page. Or whether it’s needed to clean up a page’s code.

First input delay measures the interactivity of a page. Ideally, the time of your first input delay should be within 100 milliseconds or less.

FID is the time it takes for a user to interact with your page, such as an option on a menu, a link on the navigation section, accordion text on a phone, and putting in your email address. FID takes into account how real users interact with a website.

This metric doesn’t particularly concern websites that are just full of text like a blog or news site, because in essence, the only interactive element is the scrolling up and down the page. So it’s only really applied to interactive sites, i.e. pretty much ecommerce sites.

Cumulative layout shift measures the visual stability of a page. Ideally, the time of your cumulative layout shift should be 0.1 seconds or less.

CLS tests the stability of a page as it loads, which means if some elements on a page move around as the page loads, it means that the page has a high CLS. And that is something you do not want.

Ideally, you should have the page elements to be stable as it loads, so that users don’t have to scroll down again to find the place on the page that they’re looking for – a great frustration of mine on many websites when, as soon as a page opens, I speed my way to the place where I want to view, only for it to jump back up to the top after it’s finished loading.

Why are they important?

It’s important to remember that Google’s Core Web Vitals are not the Marketing Magician’s Web Vitals – they’re not going to magically push you beyond all the competition and rocket you to number one in Google.

One sobering thought is that Google points out that page experience is just one part of factors that they use to rank a page in its search engine. And the number of these factors runs up to around 200!