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Core Web Vitals Checker

Measure and analyze Core Web Vitals metrics. Enter a URL to simulate a performance audit, or measure this page's real metrics using the Performance API.

Analyze Page Performance

Manual Metric Input

Enter your own Core Web Vitals values to get ratings and optimization tips. Useful for analyzing results from Lighthouse, PageSpeed Insights, or CrUX data.

How It Works

Core Web Vitals are a set of real-world, user-centered metrics that quantify key aspects of page experience. Google uses these metrics as ranking signals, making them critical for SEO and user satisfaction.

Core Web Vitals (2024+)
LCP — Largest Contentful Paint

Measures loading performance. The time it takes for the largest content element (image, text block, video) to become visible in the viewport.

Good: ≤ 2.5s
Needs Improvement: 2.5s – 4.0s
Poor: > 4.0s
INP — Interaction to Next Paint

Measures responsiveness. The latency of all interactions (clicks, taps, keyboard) throughout the page lifecycle. Replaced FID in March 2024.

Good: ≤ 200ms
Needs Improvement: 200ms – 500ms
Poor: > 500ms
CLS — Cumulative Layout Shift

Measures visual stability. Quantifies how much visible content shifts unexpectedly during loading. A unitless score where lower is better.

Good: ≤ 0.1
Needs Improvement: 0.1 – 0.25
Poor: > 0.25
Additional Metrics
FCP — First Contentful Paint

Time until the first text or image is rendered. Indicates when users first see content appearing.

Good: ≤ 1.8s
Needs Improvement: 1.8s – 3.0s
Poor: > 3.0s
TTFB — Time to First Byte

Time from request start until the first byte of the response is received. Reflects server and network performance.

Good: ≤ 800ms
Needs Improvement: 800ms – 1800ms
Poor: > 1800ms
FID — First Input Delay

Time from first user interaction to when the browser begins processing it. Deprecated as a Core Web Vital in March 2024, replaced by INP.

Good: ≤ 100ms
Needs Improvement: 100ms – 300ms
Poor: > 300ms
Tip: Use the "Measure This Page" button to capture real metrics from the Performance API in your browser. For production sites, use the Manual Input section to analyze data from Google PageSpeed Insights, Lighthouse, or the Chrome UX Report (CrUX).

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