Where can information about Layout Shift be found?

Layout Shift is the sudden change in the position of elements on a web page during loading, causing content jumps. You can find information about it in:

• Google Search Console: Under the "Core Web Vitals" section, data on CLS (Cumulative Layout Shift) of your site is displayed, showing pages with poor scores.
• Lighthouse Reports: The audit tool in Chrome DevTools (and in GSC) includes the CLS metric and offers recommendations for improvement.
• Web Vitals Report (Google): A specialized report providing detailed data on Web Vitals (including CLS) for your site.
• PageSpeed Insights: An online tool from Google analyzing page performance, including CLS, and providing recommendations.
• Chrome DevTools Performance Tab: Allows visualization of the rendering process and identification of layout shift moments. You can see "Layout Shifts" in the "Experience" section.
• Google Developers Blog: Frequently publishes articles and guides on Web Vitals optimization, including detailed explanations of CLS and ways to fix it.
• Layout Instability API Specification: Technical description of the API used to measure layout shifts.
• MDN Web Docs: Provides documentation on the Layout Instability API and related topics.

Examples of tools and their usage:

// Using Performance Observer to measure CLS in the browser
const observer = new PerformanceObserver((list) => {
  for (const entry of list.getEntries()) {
    if (entry.entryType === 'layout-shift') {
      console.log('Layout Shift detected:', entry);
      // Here you can send shift data to the server for monitoring
    }
  }
});

observer.observe({ type: 'layout-shift', buffered: true });

# Example of using Lighthouse from the command line
lighthouse <URL> --output=json --output-path=report.json --only-categories=performance

Lighthouse and PageSpeed Insights reports provide specific data on shift magnitude and suggest potential causes, such as images without specified sizes, dynamically added content, or fonts causing text flickering (FOIT/FOUT).