Core Web Vitals

What Are Core Web Vitals?

Google makes hundreds of changes every year. They are introducing new changes to their algorithm all the time and sometimes those changes affect ranking factors. One of the newest initiatives that were announced is Core Web Vitals. Starting in 2021, Core Web Vitals will be one of the ranking factors, and of course a part of SEO.

As you probably know the key to the long-term success of any site on the web is optimizing for the quality of user experience. You always need to monitor how your site performs and constantly keeping track of the metrics.

Google is interested in real-world experience metrics, that is, in a user’s subjective perception of the quality of their interaction with a website. They want to provide their users with fast loading times, responsiveness, and visual stability.

Core Web Vitals are the essential web vitals metrics and they correspond to an aspect of user experience. They represent the user’s subjective experience.

The Core Web Vitals are expected to evolve over time, but for now, they focus on three distinct user experience aspects: loading, interactivity, and visual stability and their corresponding metrics. For loading, we measure Largest Contentful Paint, First Input Delay is about interactivity and the topic of Cumulative Layout Shift is visual stability.

Let’s Briefly Explain the Three Signals that Comprise Core Web Vitals:

Largest Contentful Paint (LCP)

LCP is used to measure the perceived load speed by determining the time required to load the page’s main content, which means the largest image, video, or text in the viewport.

Google is looking at the largest thing in the viewport, the largest piece of content, and how fast they take to load.

You can measure LCP with both Field tools like Chrome User Experience Report, PageSpeed Insights, Search Console (Core Web Vitals report), and Lab tools such as Chrome DevTools, Lighthouse, WebPageTest.

The first couple of seconds are the most important when it comes to convincing your website visitors that they are at the right place.

Poor LCP stems from slow server response time and render-blocking JavaScript among other things.

Largest Contentful Paint - Core Web Vitals.

Cumulative Layout Shift (CLS)

With CLS, Google is checking how stable the page is. It’s used to measure the visual stability of the website by quantifying the frequency of unexpected layout shifts that users experience.

CLS measures every unexpected layout shift that occurs during the entire lifespan of the page, in order to ensure a positive user experience.

Usually, things are not stable because the image sizes often aren’t defined. There are other reasons as well but this one is number one.

When it comes to measuring CLS, that can be done in both field and lab. However, the differences between field and lab measurement results can be significant when it comes to CLS. Lab tools can only measure layout shifts, so the real users may experience more layout shifts than CLS values reported by lab tools would suggest.

Cumulative Layout Shift (CLS)

First Input Delay (FID)

FID is asking how quickly the page becomes interactive. In other words, when a user clicks on something, a button, or a JavaScript event, how fast can the browser start to process that and produce a result?

When you click on something and nothing happens, or it’s very slow, what will the user think? No one would rate that as a good user experience. So, FID measures exactly that.

FID can only be measured in the field using some of the following tools: Chrome User Experience Report, PageSpeed Insights, Search Console (Core Web Vitals report), and Firebase Performance Monitoring (beta).

Always keep in mind how important it is for your visitors to have good first impressions on your website because that’s crucial in terms of whether they will come back in the future.

First Input Delay (FID)

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