Um, its about your JavaScript...

Discover the importance of performance budgets, RUM metrics, and CPU time tracking in optimizing website performance and user experience, and learn how to overcome common challenges with third-party content and JavaScript framework Playwright.

Key takeaways
  • We’re all in the trust tree together, focusing on the performance of our sites.
  • Measuring the performance of a site with RUM (Real User Measurement) metrics is more accurate than synthetic testing.
  • The number of JavaScript calls on a page has doubled over the past 7 years, from 5 to 12.
  • Tracking CPU time and blocking CPU time is important, as it affects user experience and business metrics.
  • A performance budget is a useful tool to track and analyze the performance of a site.
  • There is no single “unicorn” metric that measures everything; instead, we need to use a combination of metrics to understand the performance of a site.
  • Tracking FID (First Input Delay) and animation frame completion rate are important metrics for measuring user experience.
  • Using third-party content can have a significant impact on page load times, and budgeting for performance is essential.
  • Measuring the performance of a site with business metrics, such as conversion rate, is important for understanding the impact of performance on the business.
  • It’s important to keep in mind the limitations of different metrics and to validate them against business metrics.
  • A show of hands revealed that many attendees have reported on performance issues related to third-party content.
  • The JavaScript framework Playwright has a built-in performance timing API.
  • Performance budgets are supported in Google Lighthouse, Webpack, and other tools.
  • Mobile devices have gotten better, but even the best mobile devices have CPU thresholds that affect performance.
  • Measuring the performance of a site with CPU metrics, such as CPU idle time, is important for understanding how CPU-intensive scripts are affecting the site.