During my two decades as a professional web developer, I’ve watched the Internet evolve from its simple and humble origins into a complex and ever-changing cocktail of browsers, devices and edicts from the major tech companies. It’s hard for anyone to keep up, and it seems like every few months, Google announces a big new change that will affect how your site is ranked in its search results and perceived by your customers.
Core Web Vitals is one of those pivotal changes. In 2021, Google will begin ranking your site — and potentially labeling it for visitors – based on whether it meets Google’s exacting standards for page speed on mobile devices. It’s an opportunity to get ahead of the competition – and you’re at risk of falling behind if you let your site languish rather than optimizing for the new rules.
I’ve spent more than a decade learning the ins and outs of optimizing WordPress, the web’s most popular content management system, and over the past year I’ve brought my site and many client sites up to lightning-speed, scoring in the coveted 90th percentile and higher on Google’s Core Web Vitals measurements. That means a better user experience and an opportunity to outdo the competition in rankings for valuable search keywords.
I will be sharing some of the chapters from my new guide, Optimizing WordPress for Core Web Vitals, in a series of blog posts — or, you can download the full guide as a PDF here.
In the guide, I’m sharing a complete overview of the process that I’ve used to optimize hundreds of WordPress sites, keeping them fast, secure and ahead of the technological curve. I want you to avoid the pitfalls and confusion that almost everyone struggles with when they first attempt to optimize their site, and skip straight to the payoff of happier users and increased organic search traffic.
What are Google Core Web Vitals?
The Core Web Vitals system is a set of measurements that Google uses to calculate the speed of your web site — resulting in a score that ranges from 0 to 100. In 2021, Google will begin using this score as a factor in your rankings, which makes Core Web Vitals a new and pivotal component to your Search Engine Optimization (SEO) goals.
While we usually think of things like keyword optimization, backlinks, meta tags and content when we discuss SEO, Core Web Vitals signals Google’s shift towards prioritizing the on-page experience in their rankings.
In addition to being newly important for SEO, the Core Web Vitals score also indicates how well your site performs on mobile devices — in particular, they’re using the mobile score from a 4G device (which is a little slower than a modern iPhone or Android device) as their baseline. That means, in Google’s eyes, you’re measured by how well you perform on a lower-end device and they care much less about how your site looks on a fast computer with a large desktop monitor.
In some ways, this is a challenge, because many sites aren’t currently optimized for mobile visitors. In other ways, it gives us some unique optimization opportunities because you can get away with your site being a little “heavier” on desktop if you really speed it up on mobile – that is, you can show more content and imagery to users with larger screens and pare it down for users with smaller screens.
Achieving excellence on your Core Web Vitals scores means you’re setting yourself up for success with SEO as well as creating a better experience for your mobile users — which will often lead to better conversion rates, or users sticking around on your site for longer when they’re coming in via social media and other sources that are heavily tilted toward mobile visitors.
Here’s a quick outline of the three primary components of Core Web Vitals. Later in the guide, we’ll dig into the six scores that influence them and ultimately generate your 0-100 score for each page.

- Largest Contentful Paint (LCP): measures loading performance. To provide a good user experience, LCP should occur within 2.5 seconds of when the page first starts loading.
- First Input Delay (FID): measures interactivity. To provide a good user experience, pages should have a FID of less than 100 milliseconds.
- Cumulative Layout Shift (CLS): measures visual stability. To provide a good user experience, pages should maintain a CLS of less than 0.1.
The links above go directly to Google’s definition of each of these measurements — and as you can see, it’s full of jargon! Even for a web developer, these metrics are kind of obtuse and difficult to understand. So, in this guide, I’ll introduce these concepts to you in layperson’s terms so you can easily assess which elements of your site need work without getting bogged down in overly fancy tech language.
Want to see how your site performs right now? Head over to Google’s PageSpeed Insights tool and give it a try. Then read on for a deep dive into how you can optimize your site, and how we can help if you get stuck.