What Are Core Web Vitals?

Google considers Core Web Vitals – along with mobile optimisation, safe browsing, HTTPS security and whether the site breaches intrusive interstitial guidelines – to be ranking signals.

With that being so, improving your own site’s Core Web Vitals is crucial for anyone looking to achieve the highest possible search engine ranking for their business.

However, Core Web Vitals are important even if you don’t take Google into account, as they are designed to ensure that a site:

  • Is user-friendly
  • Prevents any negative user experience

The Three Core Web Vitals

The Core Web Vitals metric can be broken down into three separate categories: LCP, FID and CLS (don’t worry, we’ll spell out and explain these acronyms in a minute). 

Knowing the ‘ins-and-outs’ of these categories and what they entail will give website owners a better idea of which aspects of their website they should focus on improving.

All three Core Web Vital categories are rated by Google on a scale ranging from ‘Good’ to ‘Needs Improvement’ to ‘Poor’. 

Let’s take a further look at what this means. 


LCP stands for Largest Contentful Paint, and measures a website’s total loading time in seconds. 

According to Google, the LCP of a site that loads fully in under 2.5 seconds is rated as ‘Good’, while sites that load in between 2.5 seconds and 4.0 seconds fall into the ‘Needs Improvement’. 

Any site which takes over 4.0 seconds to load is rated as ‘Poor’, and therefore needs addressing ASAP! 


FID stands for First Input Delay, and measures the site’s level and speed of user interactivity. 

It measures the time that it takes for a user to be able to interact with the site content. 

This is measured on a scale from 100ms (‘Good’) to 300ms (‘Poor’). 

Once again, anything in between 100ms and 300ms ‘Needs Improvement’. 


CLS stands for Cumulative Layout Shift, and measures the visual stability of the site. 

The level of visual stability is determined by whether:

– a site layout changes or moves unexpectedly

– this is intentional (in the case of local website pop-ups or advertisements) 


– unintentional (sporadic late-loading content) 

Anything below 0.1 is a ‘Good’ CLS score. Anything over 0.25 is ‘Poor’.

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