Core Web Vitals

What are Core Web Vitals?

Core Web Vitals are key metrics that web developers use to measure and optimize the performance of a website. They’re critical for understanding the customer experience on a site and a strong indicator of that site’s performance.  Furthermore, the better your Core Web Vitals, the better your Google search results.

Let’s break down six essential Core Web Vitals in simple terms to understand why they’re crucial for a website’s success.

What are the three pillars of Core Web Vitals?

Although Core Web Vitals metrics evolve over time, currently, there are three main pillars developers should focus on: loading, interactivity, and visual stability. Those related metrics consist of Largest Contentful Paint (LCP), First Input Delay (FID) and Cumulative Layout Shift (CLS). 

Largest Contentful Paint 

LCP measures the time it takes for the largest piece of content on a webpage to become visible. Functionally, this is how long it takes for the user to see a website as it’s meant to be presented. 

A fast LCP (page load within 2.5 seconds) ensures users discern meaningful content quickly, prompting them to begin their browsing and engagement.

First Input Delay

FID measures the time between a user’s first interaction (like clicking a button) and the browser’s response to that interaction.

FID helps assess a website’s interactivity. A low FID (100 milliseconds or less) ensures users can interact with the site without frustrating delays, leading to a positive user experience and increased user engagement.

Cumulative Layout Shift 

CLS measures the visual stability of a webpage by quantifying unexpected layout shifts of visible elements.

Ever lose your place on a page because the content shifted as it loaded? CLS is important because it reflects the consistency and predictability of the user interface. A low CLS (0.1 or less) indicates that the page layout remains stable during loading, preventing frustrating shifts that can lead to accidental clicks or a confusing user experience. 

Note that CLS is a score based on the layout shifts identified. Unlike the other Core Web Vitals spotlighted here, it isn’t measured in units of time. 

What other metrics are important to Core Web Vitals?

Besides the three main Core Web Vitals metrics, developers should also measure First Contentful Paint (FCP), Interaction to Next Paint (INP), and Time to First Byte (TTFB).

First Contentful Paint 

FCP measures the time it takes for the first piece of content to appear on the screen. FCP is crucial as it indicates how quickly users can see something happening on the page. 

A speedy FCP contributes to a perception of a fast-loading website. When users can see a page loading, they feel more inclined to stick around.

Interaction to Next Paint 

INP measures the time it takes for a webpage to respond to a user’s input, such as clicking a link, and start rendering the next page.

INP is critical for user engagement, especially on websites with multiple pages. A quick INP ensures a smooth transition between pages, preventing delays or disruptions in users’ browsing journey.

Note that FID is going out of fashion as a Core Web Vital metric. Google is replacing it with INP. While FID measures delays in user experience, INP is a more helpful metric in measuring a page’s overall responsiveness to user input. 

Time to First Byte 

The responsiveness performance metric, TTFB measures the time it takes for a user’s browser to receive the first byte of data from the server after making a request. TTFB is crucial for assessing server response times. A fast TTFB ensures users experience minimal waiting time before content starts loading, contributing to an overall speedy and responsive website.

TTFB is a common speed test metric, often touted as the be-all and end-all indicator of performance. It’s certainly one that points to a healthy, responsive site. However, in isolation, it tells us only a little about how a site loads and performs, particularly as the number of visitors to your site fluctuates around high traffic events. 

Core Web Vitals and WordPress VIP

WordPress VIP is committed to delivering both speed and performance at scale so that websites on our enterprise-grade CMS platform can delight their customers and deliver optimum web experiences, even with millions of pageviews.

Understanding and optimizing Core Web Vitals is key to delivering a positive user experience. By focusing on these metrics, web developers will enhance website performance, reduce bounce rates, and keep users engaged, ultimately contributing to the success of their online presence.

Measure the Core Web Vitals for your site.