Google Algorithm Update: Core Web Vitals

Paul Saffery - IT Director

Paul Saffery

12th February 2021

What are Core Web Vitals?

Core Web Vitals are a set of three metrics designed by Google, aimed at assessing the user experience of a website. As from May 2021, Google will start using the Web Vitals score as one of their ranking signals - an important one - for their organic search results. The underlying logic is to drive traffic to websites that provide the best user experience. There are distinct metrics depending on whether your website is displayed on mobile or desktop. Therefore, websites should be optimised for both types of devices in order to remain competitive in organic search results.

The Three Core Web Vitals Metrics

Core Web Vitals englobe the following three metrics, all to do with user perception and user experience:

Largest contentful paint (LCP): Measures the time required to render the largest content element (image or block of text) visible above the fold, i.e. before scrolling, also known as the viewport. Three factors that affect LCP are CSS, server delay time (TTFB), and client-side rendering (for example dynamic rendering using JavaScript on the client side). In order to achieve a good score (green), you should aim for an LCP below 2.5 seconds.

First Input Delay (FID): Measures the time from when a user first interacts with the page
until the time when the browser is actually able to respond to that interaction. For example, the user hovers on an image to reveal a tooltip, but the tooltip doesn’t appear immediately because the functionality is implemented by external Javascript that has not yet loaded. In order to achieve a good score (green), you need an FID below 100 milliseconds.

Cumulative Layout Shift (CLS): Measures visual stability. In order to achieve a good score (the lower the better), page elements should not shift around while the page is loading. In order to achieve a good score (green), you need a CLS below 0.1.

How to Assess Your Website’s Core Web Vitals

There are several online tools that will show your score for each of the three metrics. Among them are Google’s web.dev, Chrome’s User Experience Report and Search Console’s Core Web Vitals Report. Apart from giving you your Core Web Vitals scores, these tools will show you a list of the optimisations required to improve your score, listed from most to least relevant.

When assessing your website, do not limit your focus on your homepage only. Instead, you should optimise all pages of your website that are relevant to achieve conversions and rank well on search results. To do this, create a list containing pages representing each page type. For example: homepage, contact page, product listing page, category page, product details page, blog page and so on. The underlying logic is that all pages of the same type will probably be suffering from the same issues. Therefore, your improvements to one page will also improve all other pages of the same type.

Optimising Websites Built Using Content Management Systems

Most professional websites are developed using content management systems, both paid and open source. These platforms often make it hard to apply all the optimisations required to improve Core Web Vitals scores. This is because some of the code on the web pages comes from the core or third party modules, which you should not interfere with - otherwise the maintenance of the website could become very difficult.

For example, at SilverDisc we develop websites using Drupal and Magento. Both systems provide modules aimed at overcoming the above limitations. In the case of Drupal, one example is the Advanced JS/CSS Aggregation Module. For Magento, a popular extension is Speed Optimization Extension (WebP).

Next Steps

We encourage you to measure the Core Web Vitals for some of your website’s pages, using some of the tools mentioned above. As Google will soon be using Core Web Vitals as a ranking factor, your presence within SERPs may suffer if your website’s scores aren’t up to scratch. If you are not satisfied with your scores, and would like to discuss them with experts in the subject, contact SilverDisc.

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