Core Web Vitals represent the most important metrics for understanding the quality of a user’s experience on your ecommerce site. These standardized performance indicators have been defined by Google to quantify three critical aspects of user’s experience: loading speed, interactivity, and visual stability. Ensuring good Core Web Vital scores helps ensure healthy conversion rates and improved SEO.
Why Noibu focuses on Core Web Vitals
There have been many different metrics that can measure website performance, including Total Blocking Time (TBD), First Input Delay (FID), and more. However, ambiguity in how performance is measured often blocks ecommerce brands from making meaningful progress towards improvement.
To align with industry standards and reduce the potential for confusion, Noibu reports on the three Core Web Vitals:
- Largest Contentful Paint (LCP) – Measures page loading speed.
- Interaction to Next Paint (INP) – Measures responsiveness to user interactions.
- Cumulative Layout Shift (CLS) – Measures visual stability and layout shifts during load.
These are the key metrics Google defines for measuring website performance, and they are the only metrics considered when evaluating page experience for SEO. Standardization on these three metrics is often a critical first step in driving performance improvements across ecommerce websites.
Noibu tracks these metrics individually with each session recording and are also summarized in aggregate on the Performance Monitoring page. Each metric is measured with real user data collected during a session and is rated as Good, Improvable, or Poor based on Google’s benchmarks.
| Core Web Vital | Description | Google Benchmarks |
| Largest Contentful Paint (LCP) | The time to render the largest content element (usually an image or video). Usually, a poor LCP score is caused by oversized files, uncompressed images, JavaScript and CSS that blocks rendering, or slow server response time. |
Good: ≤ 2500 ms Improvable: ≤ 4000 ms Poor: > 4000 ms |
| Interaction to Next Paint (INP) | The time to respond to user interactions (mouse clicks, taps, and keystrokes). A faster INP indicates a more responsive page and ensures a smooth user experience. A poor INP score indicates the page may appear laggy to users. |
Good: ≤ 200 ms Improvable: ≤ 500 ms Poor: > 500 ms |
| Cumulative Layout Shift (CLS) | Instances of layout shift, where a page element changes position or size. This causes content on the page to shift and creates a poor user experience. Often, a poor CLS score is due to ads, dynamically injected content, and embeds and iframes without dimensions. |
Good: ≤ 0.1 Improvable: ≤ 0.25 Poor: > 0.25 |
How data is collected
Noibu collects Core Web Vital measurements from real user sessions to provide meaningful insights based on actual customer experiences. Unlike data derived from synthetic testing or third-party data, this approach is directly reflective of how real customers experience your website and is recognized as a best-in-class approach to measuring site performance. Our platform follows Google's standard approach of using the 75th percentile (p75) of pageviews to measure Core Web Vitals.
Limitations when measuring Core Web Vitals
Although Noibu collects web vital data from every session, technical limitations in certain browsers prevent the measurement of some vitals. The table below outlines which metrics are supported by browser:
| Web Vital |
Chromium (includes Chrome and Edge) |
Firefox | Safari |
| LCP | Supported | Supported | Unsupported |
| INP | Supported | Unsupported | Unsupported |
| CLS | Supported | Unsupported | Unsupported |
It’s also important to note that Core Web Vitals are less precise on Single Page Applications (SPAs) due to how these applications manage routing and content updates without full page reloads. This is not a Noibu limitation—Google acknowledges this as limitation of the Core Web Vitals specification itself. Despite this limitation, Google continues to rely on Core Web Vitals as a measure of performance and to inform search rankings for SPAs.
Although the absolute measurement may be less precise for SPAs, the aggregate data remains directionally accurate and highly useful for identifying performance trends.
Learn more about performance monitoring in Noibu.