How do you measure whether your website feels fast to users?

Web Vitals are a set of metrics defined by Google to measure real-world user experience on web pages. They focus on three core aspects of UX: loading, interactivity, and visual stability. These metrics affect both user experience and SEO rankings.

Largest Contentful Paint (LCP) measures loading performance—specifically, when the largest content element becomes visible. Good LCP is under 2.5 seconds. Improve it by: optimizing images, preloading critical resources, improving server response times, and using a CDN.

First Input Delay (FID) measures interactivity—the time from when a user first interacts with your page to when the browser can respond. Good FID is under 100ms. Improve it by: breaking up long JavaScript tasks, using web workers for heavy computation, and deferring non-critical JavaScript.

Cumulative Layout Shift (CLS) measures visual stability—how much page content unexpectedly shifts during loading. Good CLS is under 0.1. Improve it by: including size attributes on images/videos, reserving space for ads/embeds, and avoiding inserting content above existing content.

Interaction to Next Paint (INP) is replacing FID, measuring responsiveness throughout the entire page lifecycle, not just the first interaction.

These metrics are measured from real user data (RUM) and reported in tools like Chrome User Experience Report, PageSpeed Insights, and Search Console. Optimizing Web Vitals improves both user experience and SEO performance.