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What are Core Web Vitals and how will they impact my website?

BY TOM HART | January 29, 2021

Recently Google has been more forthcoming with announcements on how they are going to be updating their algorithms and ultimately how that is going to impact website rankings. Back in 2016, Google announced that they would be moving to a mobile-first index and more recently they have started announcing when core updates are going to happen before rolling them out.

Of course, there are still hundreds if not thousands of algorithm updates every year, many of them minor and probably not even noticed by the majority of website owners. But the larger updates are now getting announced, giving site owners chance to prepare for them and Core Web Vitals is the most recent of those announcements.

Core Web Vitals

In May 2021, what Google is calling Core Web Vitals, are going to become a ranking factor and will start impacting the SEO performance of websites. These ranking factors are another move away from traditional ‘on-page’ signals and much more focused on user experience or UX.

Three factors will contribute to a websites Core Web Vitals:

  • Largest Contentful Paint (LCP) – In simple terms, ‘how quick does a website load’.  This will be impacted by, image size, page content, on-page videos etc.
  • Cumulative Layout Shift (CLS) – Again, in simple terms ‘how long until a website is stable’. I’m sure we have all experienced where a website is loading and you go to click on a button but it suddenly move.  This happens because something else on the page has loaded and moves what you wanted to click on and you end up clicking on something else, very annoying!
  • First Input Delay (FID) – Simple terms… ’how quickly can a user interact with a website’. If you click on a button but nothing happens because the website is still loading it can be frustrating and a poor user UX.

What to do about your Core Web Vitals

Whilst that may all sound daunting Google is making it as easy as possible for website owners to see their performance and will suggest fixes that will help sites perform better. In Search Console they have a new report, ‘core web vitals’ or you can download the Lighthouse plugin which will allow users to run a report on any website.

How much of an impact will this have?

It is tough to predict how much this will shake up search results but it will bring about changes. Depending on where you get your information from, it has been estimated that as little as 15% of websites are currently ready for this update. If that is the case then and there are no improvements then it could have a very big impact on search results.

The fact that Google has given a warning that this is coming in to play is a pretty good indication that this will be a relatively large update and they thought it only right to give people fair warning.

As well as it becoming a ranking factor it has also been rumoured that Google will have some form of visual identifier, showing searchers whether a website has a good user experience or not. Even if a site ranking position doesn’t change, if searchers see a warning about poor users experience the click-through rate is almost certainly going to decline.

Next Steps

The first thing to do is to run your website through either Lighthouse or GTMetrix to understand how much work needs to be done. This will give a good starting point and show site owners where they need to focus their attentions in the coming months.

If you would like some more information or guidance on what to do next please contact us on 0203 368 8556 or


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