RUM Visualizer is a Chrome extension developed by MarketingTracer. It allows users to visualize the Core Web Vitals for any webpage. With this extension, you can easily access and understand important metrics such as Largest Contentful Paint (LCP), First Input Delay (FID), Cumulative Layout Shift (CLS), First Contentful Paint (FCP), Interaction to Next Paint (INP), and Time To First Byte (TTFB).

The extension offers a range of features for each metric. For LCP, you can get the RUM values, visualize the LCP, and break it down into components such as Time to First Byte, Resource Load Delay, Resource Load Time, and Element Render Delay. Similarly, for FID, you can get the RUM values, visualize the FID, and explore its breakdown.

CLS values can be obtained, and the breakdown can be displayed and animated. FCP values can be accessed and broken down as well. INP values can be visualized, and the breakdown can be explored. TTFB values can be obtained and broken down for analysis.

In addition to these features, the extension also provides easy debugging options. You can emulate slow network conditions (3g) and enable or disable caching for the current page. These options help in identifying and addressing performance issues.

The extension has undergone several updates, with version 1.2 adding extensive LCP information, version 1.4 introducing a left side menu and additional information about render blocking resources, and version 1.5 including code and layout improvements and page experiments. Version 1.6 brought a better INP breakdown and minor code improvements, and version 1.7 allows users to log events, long tasks, and long animation frames to the console during INP analysis.

With Core Web Vitals Visualizer, web developers and performance enthusiasts can gain valuable insights into the performance of any webpage and optimize it for a better user experience.