Core Web Vitals: LCP, INP & CLS Reference Guide Interactive reference guide for LCP, INP, and CLS Core Web Vitals metrics.

🔍

Core Web Vitals Explainer

Interactive reference guide for LCP, INP, and CLS Core Web Vitals metrics.

Select a metric

Click LCP, INP, or CLS to explore each Core Web Vital in detail.

Review thresholds

See the good, needs improvement, and poor thresholds for each metric.

Follow optimization recommendations

Apply the suggested changes to improve your LCP, INP, and CLS scores.

Loading tool...

What Is Core Web Vitals Explainer?

The Core Web Vitals Explainer is an interactive reference guide for Google's three Core Web Vitals metrics: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). These metrics measure loading performance, interactivity responsiveness, and visual stability — the three pillars of user experience that Google uses as ranking signals. This guide explains what each metric measures, the specific thresholds for good/poor scores, concrete optimization strategies, and which tools to use for measurement.

Why Use Core Web Vitals Explainer?

Interactive exploration of all three Core Web Vitals
Clear good/needs-improvement/poor thresholds for each metric
Specific, actionable optimization strategies per metric
Measurement tool recommendations
SEO impact explanation and ranking factor context

Common Use Cases

Performance Learning

Understand what each Core Web Vital measures and why it matters.

Optimization Planning

Identify specific improvements for each metric on your site.

Client Education

Explain CWV importance to clients and stakeholders.

Technical SEO

Reference guide during performance audits.

Technical Guide

LCP measures loading performance — the time until the largest visible content element renders. Good: ≤2.5s. INP (replaced FID in March 2024) measures responsiveness — the worst interaction latency throughout the page visit. Good: ≤200ms. CLS measures visual stability — cumulative unexpected layout shifts. Good: ≤0.1. Google uses field data from Chrome UX Report (real user measurements) for ranking, not lab data. All three metrics became ranking factors in June 2021 as part of the Page Experience update. While content relevance remains the primary ranking signal, CWV serves as a tiebreaker between pages with similar quality.

Tips & Best Practices

1
Focus on LCP first — it has the most noticeable impact on user experience
2
Use field data (CrUX/Search Console) not just lab data for ranking assessment
3
INP replaced FID in March 2024 — ensure your interactions are fast
4
Prevent CLS by setting dimensions on images and reserving space for dynamic content
5
Test on mid-tier mobile devices (Moto G4) for realistic performance assessment

Related Tools

Meta Tag Generator

Generate complete HTML meta tags including Open Graph and Twitter Card tags.

🔍 SEO Tools

HTTP Header Viewer

View and understand HTTP headers with SEO-relevant explanations for each header.

🔍 SEO Tools

PageSpeed Insights Guide

Comprehensive reference guide for understanding and improving PageSpeed Insights scores.

🔍 SEO Tools

Mobile-Friendly Checker Guide

Interactive checklist for mobile-friendliness with best practices and fix instructions.

🔍 SEO Tools

Frequently Asked Questions

Q Are Core Web Vitals a ranking factor?

Yes. CWV became a Google ranking factor in June 2021. They serve as a tiebreaker between pages with similar content quality.

Q What replaced FID?

Interaction to Next Paint (INP) replaced First Input Delay (FID) as the responsiveness metric in March 2024. INP measures all interactions, not just the first one.

About This Tool

Core Web Vitals Explainer is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.