October 29th 2021

Google’s Core Web Vitals explained

Well, Google has been at it again. We’ve waited a bit to post about this subject until we’ve had time to run a few tests ourselves and see what’s going on. The latest set of tools are to do with gauging page load times, Core Web Vitals. Introduced in July this year (2021) this is yet another new set of metrics to determine how well web pages perform in SERPs (search engine result pages). These Web Vitals assist in keeping businesses delivering the best web experience for their audiences.

These new metrics that makeup Core Web Vitals will continue to evolve over time. Google might add or change these metrics as they evaluate them over a longer period. Currently, though, Google are focusing on Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS).

Largest Contentful Paint (LCP)

Google created this to measure loading performance. It measures how long it takes for the largest piece of content to load onto a screen. This could be an image or a piece of text. The target is that it should load within 2.5 seconds of when the page starts loading. If this takes over 4 seconds, it is considered poor performance. Maybe those big hero banner videos will become a thing of the past

First Input Delay (FID)

This tool focuses on on-site interaction, specifically in terms of a website’s response rate. This could be a tap on a button, for instance. A good score here gives the user a sense that a site is quick to react to input and, therefore, responsive. Pages should have an FID of 100 milliseconds or less. If response rates take longer, improvements are required.

Cumulative Layout Shift (CLS)

This final metric measures the visual stability of a website, particularly in terms of layout shifts. We’ve all been on those annoying news sites when the page starts to jump around as all the different adverts are loading in. To provide a good user experience, pages should maintain CLS of 0.1 or less. If your web pages are maintaining over 0.3, action needs to be taken.

Testing Core Web Vitals

From what we’ve noticed this approach to taking these metrics as a key indicator shows a move to bolstering the mobile-first approach. These metrics have always been on our radar, the information you need can be found in Google's developer modes on Chrome and we’ve used them for a while to find bottlenecks when a site is loading.

The main difference we’ve noticed is that these measurements now have a much more immediate impact on how Google ranks your site, in SEO terms at least.

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