Core Web Vitals
Core Web Vitals are three metrics Google uses to quantify user experience: Largest Contentful Paint (loading), Interaction to Next Paint (responsiveness), and Cumulative Layout Shift (visual stability).
The recommended targets are LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1, measured on real-world traffic. They are part of how Google assesses page experience, but their bigger value is that they describe whether a site actually feels fast and stable to use.
How it works
Largest Contentful Paint measures when the biggest visible element, usually a hero image or headline, has rendered. Interaction to Next Paint measures how quickly the page visibly responds to clicks, taps and key presses throughout the visit. Cumulative Layout Shift adds up how much content jumps around unexpectedly while the page loads.
Google judges them from real visitors' Chrome data at the 75th percentile, so a page passes only when most real visits, including slow phones on mobile data, meet the target.
Example
On the Catering Prishtina build, image payload came down by 96.2%, which is the kind of change that moves LCP. On troiana.net itself, fonts are now self-hosted and preloaded and every image declares its width and height, which removes a third-party request and stops layout shift as images arrive.
Common mistakes
- Optimising a lab score on a fast laptop and ignoring field data from real phones.
- Lazy-loading the hero image, which delays exactly the element LCP measures.
- Leaving images and embeds without dimensions, so the page jumps as they load.
