Understanding Core Web Vitals with Embrace Web RUM

Core Web Vitals are a set of performance metrics created by Google to quantify key aspects of user experience on the web. Specifically, they measure how fast, stable, and responsive your website feels to real users.

There are three Core Web Vitals that matter most:

1. Largest Contentful Paint (LCP) – How long it takes the largest visible element on the page (usually an image or headline) to load. CLP should ideally be 2.5 seconds or less. 
2. Interaction To Next Paint (INP): How quickly a webpage responds to user interactions, such as clicks, taps, and other keyboard commands.  INP should ideally be 200 ms or less. In 2024, INP replaced the older Core Web Vital focused on interactivity and responsiveness, called First Input Delay (FID). This measured the delay between a user’s first interaction (like a click or tap) and the browser’s response, with a goal of less than 100 ms.
3. Cumulative Layout Shift (CLS) – How much the page content shifts around as it loads. A high CLS means jumpy pages and frustrated users. CLS is not measured in terms of duration, but rather is a layout shift “score” calculated by looking at the movement of unstable elements between two rendered frames. It’s represented as a ratio, with ideal CLS being 0.1 or less.

These metrics aren’t just vanity scores. Google uses them in its search ranking algorithm, and they’re tightly linked to user satisfaction and conversion rates.

Performance is product. In today’s digital landscape, slow or janky experiences cost you, whether that’s in lost users, lower engagement, or abandoned checkouts.

Improving Core Web Vitals ensures your end users have a better experience on your website, but that’s not the only thing. There are real commercial benefits for optimizing these scores, and a number of companies have studied and recorded this effect. 

Core Web Vitals are a key part of Google’s page experience signals, which influence how your site ranks in search results. Google prioritizes sites that deliver fast, stable, and responsive experiences—meaning pages with strong scores for metrics like LCP, CLS, and INP (formerly FID) are more likely to appear higher in rankings. While great content still matters most, performance now plays a meaningful role in how visible your site is to users, especially on mobile search. In short: better Core Web Vitals can help improve your discoverability and drive more organic traffic.

Aside from affecting site rankings, Core Web Vital scores are actually tied to more tangible business outcomes. Studies have shown that improving LCP, CLS, and FID directly correlates with higher retention and conversion: 

• A 2023 study from Adobe found marked improvements across its B2B properties after implementing Edge Delivery Services from Adobe Experience Manager Sites and improving Core Web Vital scores. This included a 40% increase in site engagement and a 14% increase in repeat site visits. Crucially, Adobe saw a direct impact on conversion – the study found a 37% increase in conversion rates for pages that included form-fills. 
• In 2021, global telecom giant Vodafone ran an A/B test specifically focused on optimizing Web Vitals. The company found that a 31% improvement in LCP led to 8% more sales, a 15% improvement in their lead to visit rate, and a 11% improvement in their cart to visit rate.
• A 2006 study and analysis done by Amazon found that every 100ms delay in page load time was associated with a 1% drop in revenue. At the time, that would have been around $107 million, but considering Amazon’s size today, this would be closer to $4 billion. 

These examples, and the numerous others that consider different aspects of page performance like load time, speed, and responsiveness, all highlight one critical truth – performance is intrinsically tied to commercial success. If it’s unsatisfactory in any way, end users will not hesitate to abandon a product and go elsewhere. 

Embrace automatically captures Core Web Vitals as part of our Web RUM offering, no extra setup required. That means you can:

• Monitor Core Web Vitals at a high level to get a pulse on overall page health, spot trends and regressions, and identify high-impact issues 
• Analyze vitals at the instance level to troubleshoot the root cause of a poor score on a page
• Correlate vitals with real user behavior, like rage taps, navigation issues, or crashes by viewing them within the context of a full Session Timeline 

Unlike traditional dashboards that provide mainly surface-level metrics, Embrace gives you the full context around what users actually saw and did. You’ll understand not just that LCP got worse, for example, but when exactly it got worse, which users were impacted, and what exactly they were doing in the lead up to a non-performant page. 

Embrace provides both an aggregated view of all Core Web Vital scores across a website’s pages. Additionally, the platform allows you to dive into any one page on your website and investigate unique instances of Core Web Vital scores that were captured for that page. 

From there, you can directly view a unique CWV score within the trail of full end User Timeline. This connects the CWV score to the rest of the events and activities that occurred across a session, so you can contextualize slow or unresponsive site behavior alongside things like networking issues or unexpected user behaviors. 

One of the most powerful aspects of Embrace’s Web RUM is its ability to pinpoint exactly why a Core Web Vital score is poor. 

Let’s take an example of a poor LCP score for a specific web page. 

Like all the other Core Web Vitals, LCP is defined and calculated by Google. What many developers don’t realize about LCP is that it isn’t a theoretical average—it’s tied to a single, specific DOM element on the page. 

Google calculates LCP based on the render time of this element, which is dynamically determined based on size and visibility during page load. This process is called attribution, and it’s essential for understanding what exactly is causing poor LCP scores.

Unfortunately, most RUM tools only report the LCP score itself—leaving teams guessing which element was responsible. That’s where Embrace comes in. Embrace’s Web RUM doesn’t just surface the metric—it identifies the exact element that triggered the LCP event for each real user session. This means developers don’t have to wade through source maps, logs, or browser tools to figure out what went wrong. They get immediate, actionable insight into the root cause of a performance issue.

By highlighting the responsible element, Embrace turns LCP from a high-level performance signal into a concrete debugging tool. Teams can finally move from “we have a slow LCP” to “this image is causing it, and here’s how to fix it”—saving time, improving UX, and boosting Core Web Vitals scores in the process.

Whether you’re optimizing for SEO, improving conversions, or simply delivering a better experience to every visitor, Core Web Vitals are metrics you can’t afford to ignore. Embrace Web RUM gives teams the visibility and context they need to both measure performance and improve these metrics with actionable data. 

If you’d like to learn more about Core Web Vitals in Embrace, or any other of our recently released Web RUM features, join our upcoming webinar. 

Or, if you want to explore Embrace for yourself, you can create an account for free.