Core Web Vitals
Core Web Vitals are Google’s set of user-experience metrics — Largest Contentful Paint, Interaction to Next Paint, Cumulative Layout Shift — that factor into search ranking.
In plain English
Core Web Vitals are three user-experience metrics Google uses to judge a page's front-end quality. LCP (Largest Contentful Paint) measures how quickly the biggest visible element loads — hero image, headline. INP (Interaction to Next Paint, which replaced FID in 2024) measures how snappy the page feels when you click. CLS (Cumulative Layout Shift) measures how much the layout jumps as things load.
Good targets in 2026: LCP under 2.5s, INP under 200ms, CLS under 0.1. The measurements come from real users via the Chrome UX Report, not lab tests — so slow servers, heavy scripts, late-loading ads, and janky animations all pile into your score. Beyond ranking impact, the metrics correlate strongly with conversion: every improvement to LCP usually moves the business number in the right direction.
Why it matters for Black Box
Black Box's marketing site is built on Astro SSG partly to keep Core Web Vitals green. Zero JS by default, images optimized at build, fonts preconnected, layout reserved so nothing shifts — all of it ships out of the box. LLM crawlers also prefer fast pages, so the same work helps GEO.
Examples
- Inlining above-the-fold CSS to hit LCP targets.
- Reserving image dimensions to prevent CLS.
- Deferring non-essential JavaScript to protect INP.