CWV

Category: Web Design

Core Web Vitals (CWV) Google

Core Web Vitals are a set of metrics defined by Google that measure key aspects of the user experience of a web page. They are part of the broader set of page evaluation metrics called Page Experience Signals.

Simply put, Core Web Vitals measure three main things:

  • Loading: How fast does the most important content load?
  • Interactivity: How quickly can the user interact with the page?
  • Visual Stability: Do elements on the page move while the user is trying to interact with them?

These metrics are extremely important because they directly affect:

  • User Experience: Fast and stable sites make users happy.
  • SEO (Search Engine Optimization): Since June 2021, Google has been using Core Web Vitals as one of the ranking factors in search results.
  • Conversions: Improved user experience often leads to higher conversion rates and better business results.

The Three Main Core Web Vitals Metrics

Here's a detailed description of each:

1. LCP (Largest Contentful Paint) – Loading Speed

  • What does it measure? The time it takes for the largest visible element in the browser window (viewport) to load and become visible to the user. This could be a large image, video, or block of text with large fonts.
  • Goal: Ensuring good user experience (green zone).
  • Good Results:
    • Good: ≤ 2.5 seconds
    • Needs Improvement: between 2.5s and 4.0s
    • Poor: > 4.0 seconds

2. FID (First Input Delay) – Interactivity

  • What does it measure? The time it takes for the browser to respond to the first interaction from the user (such as clicking a button, link, or using a custom JavaScript control).
  • Goal: Ensuring good user experience (green zone).
  • Good Results:
    • Good: ≤ 100 milliseconds
    • Needs Improvement: between 100ms and 300ms
    • Poor: > 300 milliseconds

Important Note:

As of March 2024, FID will be replaced by INP (Interaction to Next Paint). INP is a more comprehensive metric that measures the delay of all interactions, not just the first one.

3. CLS (Cumulative Layout Shift) – Visual Stability

  • What does it measure? The amount of unexpected layout shift that occurs during the page's loading process. It measures how much visible content shifts during the loading process.
  • Goal: Ensuring good user experience (green zone).
  • Good Results:
    • Good: ≤ 0.1
    • Needs Improvement: between 0.1 and 0.25
    • Poor: > 0.25

How to Measure and Improve Core Web Vitals?

Measurement Tools:

  • Lighthouse: Audit tool in Google Chrome DevTools. Useful for local testing and getting improvement recommendations.
  • PageSpeed Insights: Enter your site's URL and get results and tips for both mobile and desktop devices. Uses real data from Chrome User Experience Report (CrUX) and Lighthouse simulation.
  • Search Console (Google Search Console): The "Experience" report shows the performance of your pages in real conditions for all users who visit them. This is the most important tool as it shows your real situation in search.
  • Web Vitals Extension: Chrome extension that gives you quick feedback on the performance of the site you're visiting.

Main Guidelines for Improvement:

  • For LCP: Optimize server, use CDN, cache resources, remove unnecessary JavaScript, optimize images (next-gen formats, responsive images).
  • For FID/INP: Split JavaScript code into smaller chunks (code splitting), minimize and defer loading of unnecessary JavaScript (defer, async), use "Web Workers".
  • For CLS: Always set width and height attributes on image and video elements, reserve necessary space for dynamically added elements (e.g., ads, banners), avoid inserting content above existing content.

Summary

Core Web Vitals are specific, measurable indicators that help website owners understand and improve the actual user experience. They are directly related to how fast, responsive, and stable your site is, which in turn affects both visitor satisfaction and your visibility in search engines like Google.