Unpacking Google’s Web Tools: How PageSpeed Insights and Core Web Vitals Drive Performance

by | Jun 13, 2024 | Google Tools, Technical SEO, User Experience (UX), Web Performance Optimisation

Understanding the Difference Between Google’s PageSpeed Insights vs Core Web Vitals

In the intricate landscape of web performance optimisation, Google’s tools and metrics are crucial for developers and website owners striving to enhance user experience. Among these tools, PageSpeed Insights (PSI) and Core Web Vitals stand out as essential components. While they are often mentioned together, understanding their distinct roles and differences is vital for effective web performance management. In this blog post, we will dive into what PSI and Core Web Vitals are, how they relate to each other, and why both are indispensable for maintaining a high-performing website.

What is PageSpeed Insights (PSI)?

PageSpeed Insights is a tool developed by Google to help website owners assess and improve their site’s performance. PSI provides both lab data and field data about a page.

  • Lab Data: This data is collected in a controlled environment using predefined device and network settings. It helps in debugging performance issues as it provides detailed information about potential bottlenecks.
  • Field Data: This data is collected from real-world users. It offers insights into how actual users experience the site, which is crucial for understanding the impact of performance improvements.

PSI generates a performance score between 0 to 100, with higher scores indicating better performance. This score is based on a weighted average of various performance metrics, including First Contentful Paint (FCP), Speed Index, Largest Contentful Paint (LCP), Time to Interactive (TTI), Total Blocking Time (TBT), and Cumulative Layout Shift (CLS).

What are Core Web Vitals?

Core Web Vitals are a set of specific metrics that Google considers essential for providing a great user experience on the web. They are a subset of Web Vitals, a broader set of metrics that Google has identified as critical to all web experiences.

As of now, Core Web Vitals include three primary metrics:

  1. Largest Contentful Paint (LCP): Measures loading performance. To provide a good user experience, LCP should occur within 2.5 seconds of when the page first starts loading.
  2. First Input Delay (FID): Measures interactivity. Pages should have an FID of less than 100 milliseconds to ensure a good user experience.  * As of March 2024, Google has replaced First Input Delay (FID) with Interaction to Next Paint (INP) as a Core Web Vital, focusing on the overall responsiveness of web pages by measuring the latency of user interactions throughout the page’s lifecycle.
  3. Cumulative Layout Shift (CLS): Measures visual stability. Pages should maintain a CLS of less than 0.1 to ensure that the layout remains stable and avoids unexpected shifts.

These metrics focus on aspects of user experience that matter the most: loading speed, interactivity, and visual stability.

How PSI and Core Web Vitals Interrelate

While PSI provides a broad overview of a webpage’s performance, Core Web Vitals zero in on the most critical aspects of user experience. Core Web Vitals are a crucial component of the PSI score, but they are not the whole picture.

PSI’s performance score includes Core Web Vitals metrics but also incorporates other metrics that reflect various aspects of performance. This comprehensive approach helps diagnose a wide range of performance issues, from slow server response times to inefficient JavaScript execution.

Why Both PSI and Core Web Vitals Matter

Holistic Performance Insight: PSI offers a holistic view of a webpage’s performance by combining lab and field data and assessing multiple metrics. This helps developers identify and prioritise a range of performance issues.

Focus on User Experience: Core Web Vitals focus specifically on key aspects of user experience. By optimising for LCP, FID, and CLS, website owners can ensure that their sites are fast, responsive, and visually stable, directly impacting user satisfaction and engagement.

SEO Benefits: Google has confirmed that Core Web Vitals are a part of its ranking signals. Improving these metrics can help boost search engine rankings, driving more organic traffic to the site.

Continuous Improvement: Regularly using PSI to monitor performance and focusing on Core Web Vitals for user experience enhancements helps maintain a high standard of web performance over time. This iterative approach ensures that sites remain competitive and user-friendly in a fast-paced digital environment.


In summary, both PageSpeed Insights and Core Web Vitals are critical for optimising web performance. PSI provides a comprehensive performance overview, while Core Web Vitals hone in on essential aspects of user experience. Together, they offer a powerful framework for ensuring websites are fast, interactive, and stable, which are key ingredients for user satisfaction and SEO success. By understanding and leveraging these tools, website owners and developers can create more efficient, user-friendly web experiences.