In a nutshell, Core Web Vitals focusses on 3 ‘core’ metrics to determine an overall ‘score’ for your website. Whilst the legitimacy and accuracy of Core Web Vitals is a somewhat contentious point amongst the development community, that’s the topic of another blog post. In this article, we’ll ignore our own personal thoughts and feelings and look at what we believe are the best ways to tackle these metrics to give you the foundations to make continual improvements to your website.

If you’re new to website performance or Search Engine Optimisation, these 3 metrics are:

  • Largest Contentful Paint (LCP)
  • Cumulative Layout Shift (CLS)
  • First Input Delay (FID) (*spoiler – watch out for Interaction to Next Paint (INP) too!)

Originally released in May 2020, the biggest impacts were felt following critical updates in mid June 2021 which began to take effect from July 2021. Over a year later, we can now analyse the impact of these metrics and look to the data to understand which factors can assist in improving your end-user experience, website performance and search engine ranking.

To assess these recommendations, we are looking for impacts that we believe will have the largest real-world impact, that are relevant and applicable to most sites and that are realistic for most developers to implement.

Largest Contentful Paint (LCP)

Largest Contentful Paint, otherwise known as 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. According to the latest data figures from December 2022, only 51% of all websites meeting Google’s recommended threshold – meaning 49% of websites are below this threshold.

Cumulative Layout Shift (CLS)

Cumulative Layout Shift (CLS) or CLS for short, is another important, user-centric metric for measuring visual stability because it helps quantify how often users experience unexpected layout shifts—a low CLS helps ensure that the page is delightful. CLS has improved significantly since the introduction of Core Web Vitals in 2020, however approximately 25% of websites are yet to meet Google’s recommended threshold.

First Input Delay (FLD)

First Input Delay, or FLD, is once again, an important, user-centric metric for measuring load responsiveness because it quantifies the experience users feel when trying to interact with unresponsive pages—a low FID helps ensure that the page is usable. Most sites actually perform well for FID, but that doesn’t mean there isn’t further opportunities to improve them even further.

In addition, Google have been developing a new experimental metric called Interaction to Next Paint (INP). Interaction to Next Paint (INP) assesses responsiveness. When an interaction causes a page to become unresponsive, that is a poor user experience. INP observes the latency of all interactions a user has made with the page, and reports a single value which all (or nearly all) interactions were below. A low INP means the page was consistently able to respond quickly to all—or the vast majority—of user interactions. With many sites performing badly against INP, it is likely that this experimental metric will actually replace FID as a ‘Core Web Vital’ in the future, so getting a head start on this new metric is a wise idea.

In summary

Google have now released some additional guidance for further optimising these metrics, so if you’d like to delve a little deeper beyond our recommendations, then you can check them out using the links below.

PS: If you found this article useful or would like to add your own inputs, please feel free to comment below or share it and help us to make continual improvements to the World Wide Web.

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