What are Core Web Vitals - How do they affect my website?

What Are Core Web Vitals And How Do They Affect My WordPress Website Performance?

WordPress Performance

The user experience of your website and it’s quality of interaction are the key to success for your WordPress website. If you are a business owner, webmaster, or digital marketer that has a website, Web Vitals can help you measure the experience and also help you identify opportunities to improve your website’s usability. 

What are Web Vitals?

Web Vitals is an initiative by Google to give websites guidance for improving the user experience. This is done in conjunction with it’s Google PageSpeed Insights, a tool that Google has provided which can be used to improve every aspect of your website performance.

The idea behind the tools Google offers to measure these metrics is that you should not have to be an expert to use them. Site owners should also know that the quality of your users experience directly correlates with your website’s success, and your users will reward you with putting experience first. The best part of this approach is that you do not have to be an expert to understand the action items Google recommends, and the Web Vitals initiative means to level the playing field, and help webmasters focus on the metrics that matter the most. 

Okay, What are Core Web Vitals?

Core Web Vitals are a part of Web Vitals that is measured using Google tools. These core pieces are representative of the user experience and are measured and graded to reflect the user experience for your visitors. 

The metrics used to grade Core Web Vitals will change over time. As of right now, measurements from PageSpeed Insights are focused on 3 parts of your website’s user experience which are the loading time, time to interactivity and overall visual stability.  Having a good user experience on your website is not only about the navigation, it is also about the way your website performs across devices. Paying attention to the Core Web Vitals and their performance will help improve your experience, giving your users a higher satisfaction. 

Largest Contentful Paint

Largest Contentful Paint (LCP): measures loading performance. To provide a good user experience, the largest contentful paint should occur within 2.5 seconds of when the page first begins loading.

The length of time it takes for your website to render for the visitor is referred to as Largest Contentful Paint. This is a Core Web Vitals metric that measures when the largest content element in the viewport becomes visible. It can be used to determine when the main content of the page has finished rendering on the screen and is visible to your user.

The most common causes of a poor score in this are are slow server response times, render blocking JavaScript or CSS, slow resource loading times and client side rendering. 

First Input Delay

First Input Delay (FID): measures the time to interactivity for your website. To provide a good user experience, pages should have a first input delay smaller than 100 milliseconds. First Input Delay is a Core Web Vitals metric that is very important to the user experience of your website. It captures the user’s first impression of a site’s interactivity and responsiveness. First Input Delay is a measurement of the amount of time it takes between a user first interacting with a website and the browser is actually responding to that interaction.  This is a field metric, and it cannot be simulated.. A real user interaction is required in order to measure the response delay between action and response.

One of the main causes of a low First Input Delay score is heavy JavaScript execution. Optimizing how your websites JavaScript parses, compiles, and executes will directly reduce First Input Delay scores, giving you a better PageSpeed and usability. 

Cumulative Layout Shift 

Cumulative Layout Shift (CLS): measures your website’s visual stability. To provide a good user experience, your web pages should have a score that is less than 0.1. Cumulative Layout Shift is a Core Web Vitals metric that measures the amount of movement a page makes as elements are forced to move because another element was resized or added to the website during loading. It measures the instability of content by summing shift scores across layout shifts that don’t occur within 500ms of user input.  The most common causes of a poor Cumulative Layout Shift are images, ads, embeds, or iframes without dimensions, dynamically injected content, Web Fonts causing FOIT/FOUT and actions waiting for a network response before updating DOM. 

Layout shifts can be both frustrating and visually jarring to your visitors. Optimizing your website to ensure it has as little shift as possible can be a great way to ensure your visitors do not get frustrated, and continue using your webpage. 

How do I test the Core Web Vitals for my Website?

PageSpeed Insights

PageSpeed Insights is a tool that Google provides for aggregating reports on the performance of a page on both mobile and desktop devices. The best part about PageSpeed Insights is that it provides suggestions on how your website may be improved.

When you use it to test your website, PageSpeed Insights provides lab and field data about that webpage. The Lab data is useful for debugging performance issues, as it is collected in a controlled environment, measuring your website and server setup specifically. The problem with this approach is that it does not take into account the other variables associated with user experience. This is where field data comes in handy. Field data captures the real-world user experience and averages it over a 28 day period to provide insights into what your visitors are actually experiencing. 

Analytics and Site Speed

The Speed reports that you can find in Google Analytics is located under the Behavior > Site Speed will help you easily find the URLs of your website that may have speed or performance issues. Using this information, you can concentrate your efforts on the most impactful areas of your website, and become a serious threat to your competition. 

Other Options

There are numerous other page speed tools such as Pingdom, or GTMetrix, and they all have very useful features. In my experience, however, most people with websites are trying to rank for Google Search, so we recommend using their tools as a guiding factor. That does not mean we are recommending not using others, but PageSpeed Insights should be the end goal when optimizing your website’s user experience. 

How Can I Improve My Website’s Performance?

That’s a huge topic, one that can require lots of time and effort — even though it’s completely worth it. That being said, if you’re using WordPress to power your website, the W3 Total Cache plugin can help you easily and quickly optimize your website and user experience.  W3 Total Cache is the #1 WordPress caching plugin, with over 1.5M users and 23M downloads. Try it for yourself for free! You may also want to visit our W3 Total Cache User Guide for help configuring it for best practices.


Core Web Vitals are very important to the performance of your website both in search engine ranking, and user experience. As the world moves into the future, internet speeds and computer capability is forever improving, and we can expect to see even more focus on the usability and operability of websites and applications. 

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