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Making Sense of Website Performance Metrics for Your eCommerce Business

Google’s Core Web Vitals

In 2017, Google began publicly advocating for the importance of web performance and user experience. This focus led to the development of Core Web Vitals in 2020, a set of metrics designed to objectively measure how users interact with websites. This initiative was driven by the recognition that user expectations for fast, responsive, and stable online experiences were rapidly increasing.

Initially, Core Web Vitals consisted of three foundational metrics:

  • Largest Contentful Paint (LCP): This metric directly contributes to the Lighthouse Performance score and is considered a key indicator of page load speed. Optimizing for a good LCP is crucial for both user experience and SEO.
  • First Input Delay (FID): This metric also contributes to the Lighthouse Performance score and measures the responsiveness of your website to user interactions. Aiming for a low FID ensures smooth interaction and user engagement.
  • Cumulative Layout Shift (CLS): This metric impacts the Lighthouse Performance score and assesses the visual stability of your website. Minimizing CLS (less than 0.1) prevents unexpected layout shifts and improves user experience.

Since their introduction, Core Web Vitals have evolved significantly. In 2023, Google announced several updates, including:

  • Refining the LCP threshold: The LCP threshold was lowered from 3 seconds to 2.5 seconds, reflecting the increasing importance of fast loading times for user engagement. This emphasizes the need for websites to optimize their largest content elements for faster loading speeds.
  • Introducing LCP candidate metrics: New LCP candidate metrics were introduced to provide earlier signals of potential LCP issues. This allows developers to identify and fix problems before they impact users, improving the overall user experience.
  • Expanding the metrics to include TTFB: Time to First Byte (TTFB) was added to the Core Web Vitals group, providing another perspective on website responsiveness. This metric measures the time it takes for a browser to receive the first byte of data from a server, directly impacting page load times.
  • Continued focus on mobile-friendliness: Google continues to emphasize the importance of mobile-friendliness for Core Web Vitals. This includes ensuring that mobile websites load quickly, respond to user interactions smoothly, and maintain visual stability.
  • Improved reporting and tools: Google has improved its reporting and tools for Core Web Vitals, making it easier for developers to track their progress and identify areas for improvement. These tools include Lighthouse, PageSpeed Insights, and Search Console.
  • Increased weight in search ranking: While not explicitly confirmed by Google, it is widely believed that Core Web Vitals play an even greater role in search ranking than before. This means that optimizing for these metrics is crucial for websites aiming to achieve higher search visibility.
  • In March 2024, Interaction to Next Paint (INP) will replace FID: INP is a metric that assesses a page’s overall responsiveness to user interactions by observing the latency of all click, tap, and keyboard interactions that occur throughout the lifespan of a user’s visit to a page. The final INP value is the longest interaction observed.

These updates demonstrate Google's ongoing interest in keeping Core Web Vitals relevant and accurate in a constantly evolving digital landscape. By optimizing for these metrics, websites can achieve a strong foundation for success, both in terms of user experience and search engine optimization.

Are Core Web Vitals All I Need To Worry About?

While Core Web Vitals (LCP, FID, and CLS) are crucial for website performance, several other important metrics contribute to a positive user experience and influence Lighthouse scoring. These metrics offer valuable insights beyond initial load times and interactivity, providing a more holistic view of website performance.

Here we are getting into the nitty-gritty of website performance on a level providing granular insights for serious website optimization. With an understanding of these non-Core Web Vital metrics, you gain a deeper appreciation of the factors driving your website's performance.

  • TTI (Time to Interactive): This metric measures the time it takes for a web page to become fully interactive and responsive to user input. A good TTI is considered to be 3 seconds or less. While not officially a Core Web Vital, TTI remains an important indicator of user experience and contributes significantly to Lighthouse scoring.
  • FCP (First Contentful Paint): This metric measures the time it takes for the first bit of content to appear on the screen after user navigation. It marks the beginning of the user experience and signifies page responsiveness. A good FCP is considered to be less than 1.8 seconds.
  • TTFB (Time to First Byte): This metric measures the time it takes for a browser to receive the first byte of data from the server. It reflects server responsiveness and directly impacts page load initiation. A good TTFB is considered to be less than 200 milliseconds.
  • TBT (Total Blocking Time): This metric measures the total time the main browser thread is blocked by long-running tasks, impacting responsiveness. A good TBT is considered to be less than 300 milliseconds.
  • LCP All Frames: This metric measures the largest content element within the entire page, including content within iframes. It provides a broader view of the most impactful content and its loading time. A good LCP All Frames is considered to be less than 2.5 seconds.
  • Speed Index: This metric measures how quickly the page content becomes visually complete, considering the time and visual weight of each element. A good Speed Index is considered to be less than 4.3 seconds.
  • First CPU Idle: This metric measures the time it takes for the main browser thread to become idle after page load. A longer time indicates potential issues affecting page responsiveness. A good First CPU Idle is considered to be less than 50 milliseconds.
  • TTI-Mobile: This metric measures the time it takes for a page to become interactive on mobile devices, specifically. Optimizing for TTI-Mobile is crucial for a positive mobile user experience. A good TTI-Mobile is considered to be less than 3.5 seconds.

Remember: while these metrics are not officially Core Web Vitals, they still play a significant role in Lighthouse scoring and contribute to a complete performance picture. Addressing them alongside the Core Web Vitals ensures your website excels across various metrics and delivers a consistently positive user experience.

Free Site Performance Tools You Can Use Now

  • Google PageSpeed Insights: This is a popular tool that provides a comprehensive analysis of your website's performance on both desktop and mobile devices. It generates reports that include metrics such as First Contentful Paint (FCP), Largest Contentful Paint (LCP), Time to Interactive (TTI), and Cumulative Layout Shift (CLS). PageSpeed Insights also provides recommendations on how to improve your website's performance.
  • GTmetrix: This tool provides a similar analysis to PageSpeed Insights, but it also includes additional features such as video capture of your website's loading process and waterfall charts that show the timing of each resource request. GTmetrix offers a free plan that allows you to test one URL per day.
  • Pingdom: This tool provides detailed performance reports that include metrics such as load times, page size, and individual resource timings. Pingdom also offers a free plan that allows you to test one URL per month.
  • WebPageTest: This tool allows you to test your website from multiple locations around the world and provides detailed performance reports that include metrics such as First Byte Time (TTFB), FCP, LCP, and TTI. WebPageTest also offers a free plan that allows you to test one URL per day.
  • Chrome DevTools: This is a built-in developer tool in the Google Chrome browser that provides a wide range of features for evaluating website performance. These features include:
    • Lighthouse: This tool provides a comprehensive analysis of your website's performance and generates reports that include metrics such as FCP, LCP, TTI, and CLS.
    • Performance panel: This panel provides a detailed timeline of your website's loading process and allows you to identify bottlenecks.
    • Network panel: This panel shows the timing of each resource request and allows you to identify slow resources.
  • Lighthouse CI: This tool allows you to integrate Lighthouse into your continuous integration (CI) pipeline to automatically test your website's performance every time you push code changes. This can help you identify performance regressions early and fix them before they impact your users.
  • Measure: This tool provides a simple way to measure the performance of your website from your mobile device. It generates a report that includes metrics such as FCP, LCP, and TTI.

Tools like Google Lighthouse help analyze your website and identify areas for improvement. By focusing on Core Web Vitals, you can build a strong digital foundation and achieve online success.

What’s the Difference Between Core Web Vitals and Lighthouse Scores?

Lighthouse Scoring Categories are a representation of multiple aspects of a website that includes consideration of the site’s core web vitals plus other factors:

Lighthouse Score Categories are:

  • Performance: This score is heavily influenced by the Core Web Vitals, particularly LCP and FID. It also considers other performance metrics like First Contentful Paint (FCP) and Time to First Byte (TTFB).
  • Accessibility: This score focuses on ensuring your website is accessible to users with disabilities. It checks for proper use of HTML elements, ARIA attributes, and keyboard navigation.
  • Best Practices: This score evaluates your website's adherence to SEO best practices, including efficient resource loading, mobile-friendliness, and proper use of structured data.
  • SEO: This score assesses the search engine optimization potential of your website, including meta descriptions, title tags, and internal linking structure.
  • PWA (Progressive Web App): This score measures your website's ability to function as a standalone app, including offline availability, push notifications, and home screen installability.

While Core Web Vitals are crucial, they are not the sole factors influencing Lighthouse scores. Optimizing for other categories like Accessibility and Best Practices can further improve your overall website quality and user experience.

When you use Google’s Lighthouse tool, you also get detailed suggestions for improvement in each category, helping you identify specific areas for optimization.

Regularly monitoring your Core Web Vitals and Lighthouse scores across key areas of your website (not just the homepage) is essential to ensure your website remains performant, accessible, and user-friendly.

How Site Performance Drives Enterprise Success

Optimizing your website to score higher in each of the Core Web Vitals (or Google Lighthouse) categories is crucial for enterprise businesses. A fully optimized site will often see positive impacts in these areas:

  • SEO: SEO is a complicated mess of levers for you to discover, prioritize and pull with the hopes of having an impact. One area that has proven time and again to have a direct impact on SEO is your site’s speed and usability. Core Web Vitals, leading to higher search engine rankings and increased organic traffic.
  • Improve user experience: Fast-loading pages, responsive interactions, and visual stability keep users engaged and convert them into loyal customers.
  • Enhance mobile optimization: Core Web Vitals are essential for mobile-friendly websites, which is crucial in today's mobile-first world.
  • Build brand reputation: A well-optimized website with good Core Web Vitals builds trust and strengthens your brand image.

By focusing on Core Web Vitals, you can unlock the full potential of your digital strategy and achieve sustainable success.

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