What are Core Web Vitals?

With the heavy shift to digital over the past few years, user experience — including availability, performance, and usability — now defines website success along with other vital business outcomes. To ensure consistent and positive user experiences, organizations need metrics that offer measurable, repeatable insight into the user experience from the moment users arrive on a website from a mobile or desktop device. Core Web Vitals (CWVs) are a set of metrics defined by Google to help measure user experience at scale.

To avoid customer churn and drive the best possible business outcomes with Core Web Vitals, it is imperative to understand their growing impact, what they mean for organizations, and how to leverage these insights to simplify web optimization efforts.

Core Web Vitals are three key metrics of web page performance that measure a page’s loading performance, interactivity, and visual stability. They are part of Web Vitals, a quality standards initiative by Google that helps web developers deliver great user experiences.

To quantify user experience (UX) and help organizations address potential issues, Google created the set of Core Web Vitals that measure those three key areas of impact across all pages. The metrics are defined as Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Interaction to Next Paint (INP).

It's essential to recognize that CWV currently reflects Google's perspective on the most effective way to assess UX quality. As that changes over time, updates to these signals should be expected. For example, Google initially included First Input Display (FID) as one of the three Core Web Vitals when it introduced them in 2020 but replaced FID with Interaction to Next Paint in 2024.

Although there are various metrics that can and should be utilized to measure and enhance user experience (UX), Google emphasizes Core Web Vitals (CWV) as the primary focus for rewarding search rankings and determining website UX success. Essentially, this means that Google continues to push the priority of page speed in the context of its search results and rankings. One reason for this focus is the impact of page speed on user experience. If page load times increase from 1 to 3 seconds, bounce rates increase by 32%. If sites take 6 seconds to load, bounce rates mushroom by 106%.

With the integration of such page experience signals into Google's algorithm, it is essential for organizations to evaluate their current user experience and pinpoint areas for improvement.

LCP measures loading performance by evaluating how long it takes for the largest image or text block on your page to load. Ideally, the LCP should occur within 2.5 seconds of initial page loading.

This primary paint is negatively affected by four factors:

• Slow server response times
• Resource load times
• Client-side rendering
• Render-blocking of JavaScript and CSS

This metric focuses on visual stability by measuring the unexpected movement of layout elements — such as images, ads, links, or buttons — during the entire lifespan of the web page. A shift occurs whenever a visible element changes position from one rendered frame to the next. Ideally, pages should maintain a CLS score of 0.1 or less.

While an occasional shift may not seem especially problematic, even the slightest layout movement can be extremely detrimental to customer experience. As an example, imagine a customer shopping online with 56 items in their cart. If this customer went to remove certain items from the cart but accidentally clicked on “submit order” due to an immediate layout shift caused by a pop-up advertisement, their shopping experience would be rather frustrating.

Common causes of CLS include:

• Images without dimensions
• Ads, embeds, and iframes without dimensions
• Dynamically injected content

Finally, INP — the successor metric to First Input Delay (FID) — accounts for overall responsiveness, measuring the latency of user interactivity (clicks, taps, keyboard strokes). The actual INP result is the longest interaction measured. For websites, a “good” INP is less than 200 milliseconds.

INP is primarily caused by heavy JavaScript execution. The browser cannot always keep up with user input while it is preoccupied with parsing large JavaScript associated with certain webpage functions.

While Core Web Vitals are three measurements of website success, there are other web vitals that developers should also consider when optimizing their sites. Improving these vitals can help facilitate website performance and diagnose issues with Core Web Vitals.

Time to First Byte (TTFB)

Measures the time between when a user makes a web page request and when the user’s browser receives the first byte of the page from the server

First Contentful Paint (FCP)

Measures how long it takes the browser to first render content from the document object model (DOM)

Total Blocking Time (TBT)

Measures how long a web page is blocked from responding to a user’s input

Time to Interactive (TTI)

Measures the total amount of time it takes for an entire webpage to become capable of responding to user input

Speed Index

Measures how quickly content becomes visibly displayed on a user’s screen during page load

Although these metrics are not part of Core Web Vitals, they still are major factors in determining the general health of your website. Additionally, improving these elements may help enhance your overall Core Web Vitals scores.

Now that we grasp the concept of Core Web Vitals, let's explore how we can leverage them to enhance business outcomes.

Consider an ecommerce website: poor UX and high bounce rates do more than frustrate customers; they can mean the difference between securing a sale and losing a cart, directly affecting the bottom line. By achieving strong scores in Core Web Vitals—indicating improved site performance and user experience—ecommerce businesses can boost their search rankings, reduce cart abandonment, and increase conversion rates.

The first step in enhancing Core Web Vitals is to establish a baseline of the site's current performance in these areas. Once this foundation is set, the focus should shift to improving those metrics. To achieve this, organizations need comprehensive visibility into their Core Web Vitals scores.

Dynatrace complements Google Core Web Vital measurements with insights across your applications from front to back end.

With zero configuration, you can leverage all three Core Web Vital metrics in Dynatrace and get details with just a few clicks. To accelerate your ability to get full value from CWV metrics and other digital experience monitoring (DEM) in Dynatrace, the Dynatrace Business Insights team provides expertise and advanced technology. They can provide precise answers about how to apply CWVs at scale, know where to focus first when pages fail, and clearly communicate this data to business stakeholders.

With user experience now an essential aspect of improved search rankings to help your business reach target markets, CWV-driven page optimization is critical to create measurable, sustainable change.