Core Web Vitals Test

Measure the metrics Google uses to evaluate user experience: LCP, INP and CLS. These vitals directly impact your search rankings.

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What Are Core Web Vitals?

Core Web Vitals are a set of specific, Google-defined metrics that measure key aspects of user experience on the web: loading performance, interactivity, and visual stability. Google introduced them as ranking signals, meaning they directly influence where your pages appear in search results.

There are three Core Web Vitals, each measuring a distinct aspect of the user experience, and each with a "good," "needs improvement," and "poor" threshold.

The Three Core Web Vitals

LCP - Largest Contentful Paint

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

  • Good: ≤ 2.5 seconds
  • Needs improvement: ≤ 4.0 seconds
  • Poor: > 4.0 seconds

How to improve: Optimize image serving, preload key resources, eliminate render-blocking CSS/JS, and use a CDN.

INP - Interaction to Next Paint

Measures responsiveness: the time from when a user interacts with the page (click, tap, keypress) until the browser paints the next visible update.

  • Good: ≤ 200 milliseconds
  • Needs improvement: ≤ 500 milliseconds
  • Poor: > 500 milliseconds

How to improve: Reduce JavaScript execution time, break up long tasks, and avoid third-party scripts that block the main thread.

CLS - Cumulative Layout Shift

Measures visual stability: how often and how much elements shift around on the page as it loads, which is disruptive and frustrating for users.

  • Good: ≤ 0.1
  • Needs improvement: ≤ 0.25
  • Poor: > 0.25

How to improve: Reserve space for images and ads, use fixed dimensions for embeds, and avoid inserting content above existing content.

Why Do Core Web Vitals Matter?

Ranking Factor

Core Web Vitals are an official Google ranking signal. Pages that pass all three vitals rank better.

User Experience

Faster, stable, responsive sites keep users engaged, reduce bounce rates and improve satisfaction.

Business Impact

Improved vitals correlate with higher conversion rates, more sales, and better ad performance.

Additional Web Vitals You Should Track

  • First Contentful Paint (FCP): When the first content paints.
  • Time to First Byte (TTFB): Server response time.
  • Total Blocking Time (TBT): Main thread blocking between FCP and TTI.
  • Speed Index: Visual completeness over time.

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