Core Web Vitals are a set of real-world, user-centered metrics defined by Google that measure key aspects of the user experience: loading performance, interactivity, and visual stability. They are an official Google ranking factor since 2021.
The Three Core Web Vitals
- LCP (Largest Contentful Paint) — Measures how quickly the largest visible content element loads. Target: under 2.5 seconds.
- INP (Interaction to Next Paint) — Measures responsiveness when users interact (click, tap, type). Target: under 200 milliseconds. (Replaced FID in March 2024.)
- CLS (Cumulative Layout Shift) — Measures how much the page layout shifts unexpectedly during loading. Target: under 0.1.
Impact on WordPress
Common WordPress issues that hurt Core Web Vitals:
- LCP: Large unoptimized hero images, slow server response, render-blocking CSS/JS.
- INP: Heavy JavaScript from plugins, excessive DOM size, long main thread tasks.
- CLS: Images without dimensions, ads loading late, web fonts causing layout shifts.
What InspectWP Checks
InspectWP analyzes factors that affect Core Web Vitals, including HTTP compression, HTTP/2 usage, image optimization, JavaScript and CSS file counts, and HTML size.