SEO & Metadata
What are Core Web Vitals?
A set of three Google-defined page-experience metrics (LCP, INP, CLS) that measure load speed, interactivity, and visual stability, used as ranking signals.
Also known as: CWV
Core Web Vitals are Google's public KPIs for "is this page good to use?" LCP (Largest Contentful Paint) measures how long until the main content is painted (target: under 2.5 seconds). INP (Interaction to Next Paint, replaced FID in 2024) measures how snappy the page feels when interacted with (target: under 200ms). CLS (Cumulative Layout Shift) measures unexpected visual jumps (target: under 0.1).
The metrics are scored at the 75th percentile across real users (not synthetic tests) and read from the Chrome User Experience Report (CrUX). Pages that pass all three thresholds get a small ranking boost on Google search; pages that fail badly get a small penalty. The bigger effect is on conversion: every 100ms of LCP improvement reliably moves the bottom line on commerce sites.
For brand and marketing pages, the work is well-understood: optimize the LCP image (right format, right size, preloaded), minimize JS execution on the critical path, reserve space for images and embeds to avoid CLS, and ship interactive UI in a way that does not block the main thread. Frameworks like Next.js and Astro do most of this by default.
In the wild
- →A team converting their hero image from PNG to WebP and adding
fetchpriority="high"to drop LCP from 3.4s to 1.8s - →An ecommerce site reserving an aspect ratio on every product image to take CLS from 0.32 to 0.04
- →A monitoring dashboard tracking LCP, INP, and CLS at p75 from real user telemetry, not just a Lighthouse run
How Brand.dev uses core web vitals
Endpoints in the Brand.dev API where this concept comes up directly.
FAQ
When did INP replace FID?
March 2024. INP is a more honest measure: it captures the worst single interaction on the page, while FID only measured the first one.
How much do Core Web Vitals affect ranking?
Modestly, Google has confirmed they are a tiebreaker rather than a primary signal. The conversion impact (faster page = more revenue) usually justifies the work on its own.
Lab data vs field data?
Lab data (Lighthouse, WebPageTest) is reproducible but synthetic. Field data (CrUX, real user monitoring) is what Google uses for ranking. Optimize against the field; use lab tools to debug.