The Performance API is a set of standards for measuring and evaluating performance metrics with JavaScript. This article demonstrates how to use the Performance API to generate performance metrics directly in the DOM to create your own reporting. Chromium-based browsers have the best support for all Core Web Vitals (CWV) properties. Firefox offers partial support.

The blog post discusses the latest enhancements to the Chrome DevTools Performance panel, specifically focusing on monitoring Core Web Vitals. It highlights a series of new features aimed at improving the user experience for developers working on performance optimization. One of the key updates is the introduction of real-time local Core Web Vitals performance metrics, which allows developers to see how their local environment performs without needing to record sessions. This feature provides immediate feedback on metrics such as Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Interaction to Next Paint (INP), all of which are crucial for assessing user experience. The metrics are displayed in a color-coded format, making it easier to identify performance issues as they occur. Additionally, the Performance panel now integrates real-user experience data from the Chrome User Experience Report (CrUX) API. This data provides a comparative analysis between local performance and actual user experiences, helping developers prioritize their optimization efforts based on real-world usage patterns. The panel allows users to set up this feature easily, ensuring that the data reflects the most relevant conditions for their specific web pages. To further enhance the debugging process, the blog outlines recommendations for configuring the local environment to better simulate real user conditions. This includes suggestions for CPU and network throttling, which can help developers identify performance bottlenecks that may not be apparent in a typical development setup. The ability to emulate different device types and network conditions is emphasized as a way to uncover issues that could affect user experience. The post also introduces tools for reproducing performance issues, such as an interaction log that records user actions in real-time, providing insights into how these actions impact performance metrics. This feature allows developers to pinpoint slow interactions and understand their context within the page. In conclusion, the blog emphasizes the importance of grounding performance workflows in both real-time local data and real-user data. By leveraging these new features, developers can make more informed decisions about where to focus their optimization efforts, ultimately leading to a better user experience. The post encourages users to explore these new capabilities and provide feedback, indicating that further improvements to the Performance panel are on the horizon.