Understanding data and metrics reported for Web Vitals in GA4
LCP (Largest Contentful Paint) directly measures how quickly the largest piece of content on a webpage becomes visible to the user, essentially indicating how fast a page appears to be loading and providing a key signal to users about the page's usefulness, impacting their perception of the loading speed and ultimately affecting user experience and SEO ranking.
First Contentful Paint (FCP) is a crucial web vital metric because it measures the time it takes for the first bit of content to appear on a webpage, signifying to the user that the page is loading and providing an immediate visual feedback, which directly impacts the perceived loading speed and user experience, potentially influencing how long a user stays on the page.
FID (First Input Delay) directly measures how quickly a webpage responds to a user's first interaction, like clicking a button or link, determining how responsive and interactive a page feels to the user upon initial engagement, significantly impacting the first impression of a website and overall user experience.
INP (Interaction to Next Paint) is a web vital metric because it directly measures how quickly a website responds to user interactions, significantly impacting user experience by showing how fast a page visually updates after a user clicks or taps something, essentially determining whether a site feels responsive and user-friendly; a good INP score leads to a smoother experience and higher user engagement.
CLS (Cumulative Layout Shift) directly measures a webpage's visual stability, indicating how much the layout shifts unexpectedly while loading, which can significantly impact user experience by causing frustration when elements move around while they are trying to interact with the page, like accidentally clicking the wrong button due to a sudden layout change; a lower CLS score signifies better visual stability and a more positive user experience.
Time to First Byte (TTFB) is a metric that measures how quickly a server begins sending data to a user after a request is made, essentially representing the initial loading time and significantly impacting a user's perception of website speed; a low TTFB indicates a fast response, leading to a better user experience while a high TTFB can result in perceived slowness and potentially lost visitor.
The Metric Values are in milliseconds (1sec = 1000msec) for LCP, FCP, FID, INP and TTFB and a score for CLS.
The Avg. CWV Value is a calculated metric that is calculated by dividing {Metric Value} by {Event count}.
The value thresholds for each Core Web Vitals events are displayed below:
