Technical SEO · Glossary
What are Core Web Vitals?
Core Web Vitals are Google's metrics for real-user page experience: Largest Contentful Paint (loading, good at 2.5 seconds or less), Interaction to Next Paint (responsiveness, good at 200 ms or less) and Cumulative Layout Shift (visual stability, good at 0.1 or less).
Written by Noor KhanWhy Core Web Vitals matters
They're part of Google's page experience signals, and more importantly, slow or jumpy pages lose visitors and conversions. Passing them rarely creates rankings by itself, but failing badly can hold good pages back.
How Core Web Vitals works
- Metrics come from real Chrome users (field data) at the 75th percentile.
- INP replaced First Input Delay as a Core Web Vital in March 2024.
- Search Console groups URLs by template and shows which fail.
How to apply it
- Optimize and properly size the largest above-the-fold image or text block.
- Reduce and defer JavaScript to improve responsiveness.
- Reserve space for images, embeds and ads to prevent layout shifts.
- Fix issues per template, not page by page.
Example
On this site, replacing a 187 KB hero portrait with a correctly sized 9 KB WebP version cut the weight of the largest above-the-fold image by about 95%, the single biggest LCP win available.
Common mistake
Chasing a perfect lab score in PageSpeed Insights instead of fixing what real users experience in the field data.