Six Things You Need To Know About Core Web Vitals

Six things you need to know about Core Web Vitals

In May 2020 Google announced its new ranking factor, Core Web Vitals, a set of user-focused metrics designed to improve user experience. Google began rolling out Core Web Vitals in June 21, with the expectation that they would be completed by the end of August.

1. What are Core Web Vitals?

What are Core Web Vitals

Each of the Core Web Vitals focuses on a specific aspect of user experience.

Largest Contentful Paint (LCP)

LCP looks at how long it takes for a web page to load. It acts as a timer of how long it takes for large content items to load, such as an image, video or graphic. A good LCP is 2.5 seconds or less. Anything over 4 is categorised as poor.

First Input Delay (FID)

FID measures interactivity, or the length of time it takes for a web page to respond to a user’s first interaction. This might be tapping on a button. A First Input Delay of 100 milliseconds or less is given a good ranking. Anything over 300 milliseconds is categorised as poor.

Cumulative Layout Shift (CLS)

CLS measures how quickly a web page stabilises by examining whether all elements load at the same time or if any lag behind. This can cause a user to click on the wrong element. A ranking of 0.1 is considered good while anything above 0.25 is categorised as poor.

2. How can you measure Core Web Vitals?

How can you measure Core Web Vitals?

There are many tools at your disposal to measure the Core Web Vitals of your site. Here are some you may want to look at:

  • Web Vitals Open Source Library The Web Vitals Library measures the Web Vitals metrics on real users, in a way that accurately matches how they’re measured by Chrome.
  • Chrome Web Vitals Extension This Chrome extension measures the three Core Web Vitals in the same way as they’re measured by Chrome and reported to other Google tools.
  • PageSpeed Insights A full-service measuring tool that uses both field and lab data, offering advice on what can be improved.
  • Lighthouse Another tool for monitoring performance with some audits that PageSpeed Insights doesn’t offer.
  • Google Search Console You can access your Core Web Vitals report through the Google Search Console ‘enhancements’ tab. It analyses all the URLs that are indexed and categorizes them as good, needs improvement or bad.

3. What causes Core Web Vital poor rankings?

Each of the three Core Web Vitals suffers from a range of issues that affect their ranking:

 Largest Contentful Paint

  • Slow server response times
  • Render-blocking JavaScript and CSS
  • Slow-loading resources
  • Client-side rendering

First Input Delay

  • Long tasks that block the browser’s main thread
  • JavaScript heavy execution times and inefficient chunking
  • Third party scripts such as tags and analytics
  • Blocked main thread

Cumulative Layout Shift

  • Changes to the position of a DOM element (heading, title, body tag etc)
  • Changes to the dimension of a DOM element
  • Addition or removal of a DOM element
  • Animations that affect layout

4. Tips for improving Core Web Vitals

There are measures you can put in place to improve your Core Web Vitals.

To improve Largest Contentful Paint, you need to optimise your server. If this isn’t possible, optimise the size of your image files. Google’s WebP format is becoming popular with developers for improving this area of user experience. Another tip is to eliminate images above the fold on mobile to allow the page to display just text in the initial view.

First Input Delay is affected largely by long tasks. Google’s recommended run time is less than 50 milliseconds. Large pieces of script usually lead to long tasks so these need to be optimised or broken up into smaller chunks.

To avoid poor Cumulative Layout Shift, there needs to be enough space available for images to stop a page from moving around after the user thinks it is loaded. For each image, a block that covers its dimensions must be reserved and it must fit the layout of the page. Without these parameters, an image can nudge other pieces of content around the page.

5. Will Core Web Vitals cause a drop in rankings?

Core Web Vitals are just three of hundreds of signals that Google uses to determine web page rankings. If a page has great, relevant content it may still rank highly but it is advisable to strive to achieve the best Core Web Vitals performance score you can, as this is the new ranking that Google is focussing on. Always remember though, that factors used in rankings change in importance over time so you should monitor any Google ranking updates.

6. Are there other benefits to meeting core Web Vitals?

Yes! Let’s go back to the beginning of this article to remind ourselves of what the Core Web Vitals are for – an improved user experience. A great experience on your site can lead to increased conversions.

You can also earn a Google Core Web Vitals icon against your website in search results.

Why Choose Breeze Development?


Breeze Development are experts in web design and digital marketing. Contact us today for an informal chat about optimising your site to improve your ranking and conversions.