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Core Web Vitals: What they are and why they’re important

Page Experience ranking algorithm

Page Experience is a set of signals Google uses to measure how usable a website is and how well it delivers information to the user. It’s not the only signal Google uses to rank pages (there’s currently around 200 of those). From May 2021, these signals are set to include Core Web Vitals. Websites that don’t keep to the criteria will be missing out on ways to improve their rankings.

What are Core Web Vitals?

In May 2020, Google announced Core Web Vitals, a set of metrics related to the speed, stability, and responsiveness of a website. In short: how user-friendly any given website is.

Core Web Vitals are part of Google’s user experience metrics. They measure dimensions of usability such as load time and how easy (or difficult) it is for a user to navigate and interact with the website. Most of us have been frustrated when we accidentally tap something on our mobile devices when browsing because a block of text or an image has shifted. That’s called stability of content (or lack of in that scenario!) and this is included in Core Web Vitals metrics.

Let’s get specific.

What will Core Web Vitals be looking at specifically?

Firstly, it’ll look at the time it takes for the largest image or block of text content to load. This is known as Largest Contentful Paint (LCP). An ideal LCP measurement is 2.5 seconds or faster.

Then there’s First Input Delay (FID) which measures the time from when a user first interacts with your site (by tapping a button, clicking a link, etc) to the time the browser responds to that interaction. An ideal FID measurement is less than 100 ms.

Finally there’s Cumulative Layout Shift (CLS). This is what we mentioned above; when you’re reading an article and suddenly something moves on the page. You’ve lost your place or you’ve tapped a link or a button you didn’t want to click. Frustrating!

You’ve guessed it! CLS is the unexpected movement or shifting of elements within a page while it’s still downloading. A good CLS measure is a score of less than 0.1.

How will they be used?

These new signals will be combined with the existing search signals for page experience which include mobile friendliness, safe browsing, HTTPS security and no intrusive interstitials (pop-ups used in an inappropriate way).

From May 2021 search signals for page experience will look like this:

  • Loading – Largest Contentful Paint (LCP)
  • Interactivity – First Input Delay (FID)
  • Visual Stability – Cumulative Layout Shift (CLS)
  • Mobile Friendly
  • Safe Browsing
  • No Intrusive Interstitials

What do I need to do to prepare for the Core Web Vitals update?

The first thing on your to-do list should be checking to see how your site is impacted by these metrics. You can do this in the Google Search Console profile for your website. If you need to learn more about the Google Search Console, you can do some homework on the Google support page.

Many of the issues that’ll need to be addressed as a result of this update will require technical knowledge or access to a developer to resolve. But, here’s some things you should be thinking about:

Largest Contentful Paint (LCP)

One of the most effective ways to improve LCP is to optimise content for the device that’s requesting it. LCP can improve by more than 60% by making sure that your content is optimised for both desktop and mobile devices. There’s little worse than visiting a website on your smartphone that hasn’t been optimised for mobile.

First Input Delay (FID)

Websites that are code-heavy will have a long FID. Code splitting can be used to prioritise what loads on the page. If you don’t have the technical knowledge to work with Javascript to implement best practices, this is where bringing in an expert will be beneficial to you. Feel free to learn more about code splitting in Google’s Code Lab. Make sure you know what you’re doing before making changes to your code. You may end up doing more damage than good!

Cumulative Layout Shift (CLS)

Not all shifts in the layout of your page are bad. If a shift is user-initiated then it’s not a bad thing. Google recognises this. Any shift that happens within 0.5s second (500ms) of the last user interaction will not be counted in your Cumulative Layout Shift score. Unexpected shifts are what will cause you problems.

Things to take a look at when trying to improve your CLS score are the fonts you’re using, the placement of any ads on the page, the dimensions of your images, and any embedded content from other sources like YouTube.

Mobile Friendly 

Research carried out by Google found that 53% of mobile users abandon sites that take over 3 seconds to load. More than half the world’s web traffic is now happening on handheld devices. Responsive designs and mobile friendly websites are vital. Ensure that your images are optimised for mobile and consider using Gzip Compression to reduce file size on your website. The latter can get technical so consider calling in the professionals!

Safe Browsing 

Make sure your webpage doesn’t contain any malicious content, like malware. Keep your software up to date and your passwords strong to help prevent your website from hacking.


HyperText Transfer Protocol Secure (HTTPS) is an encrypted version of HTTP. This is what gives your website the lock icon on your browser’s address bar. This means your website is using an encrypted connection. This protects the communication between your browser and server from being intercepted and tampered with by attackers, protecting your users’ sensitive data like passwords and bank details. You can learn more about securing your site with HTTPS 


No Intrusive Interstitials

Pages that use intrusive interstitials (AKA pop-ups) provide a poor user experience. That doesn’t mean all interstitials are bad. They can be used to offer a sign-up form or special offer to a customer at exactly the right time of the customer’s journey through your website. Other times, they can be used in a negative way by covering up content that the user is on your website looking for. It’s important to use pop-ups tastefully because if they’re intrusive your rankings can be negatively affected. You can learn more about creating mobile friendly pop-ups here.

The takeaway

Page Experiences is all about enabling users to get more engaged with your content. It’s about making it easy for the user to find the information they need and the websites they’re looking for. And let’s face it, the more a user enjoys the experience of being on your website, the more likely they are to buy from you. If your website is performing badly and takes an age to load, then you’ll leave a bad taste in the mouth of a potential customer. Getting ahead and implementing changes that can improve the user experience of your website is a win-win. It improves your SEO ranking and it keeps your customers happy.

As we’ve said before, SEO is constantly evolving. Core Web Vitals will be no different and Google plans to incorporate more Page Experience signals yearly to match evolving user expectations.

How will your business be adapting to make sure you don’t lose out on traffic to your website? Working with an agency like Bobble Digital can be invaluable when it comes to preparing for updates that Google brings into play. Contact us today to discuss what we can do for you to make sure your website is ready to roll out the changes.