It's exciting working at SpeedCurve and pushing the envelope on performance monitoring to better measure the user's experience. We believe when it comes to web performance it's important to measure what the user sees and experiences when they interact with your site. A big part of our focus on metrics has been around rendering including comparing TTI to FMP, Hero Rendering, and critical blocking resources.
The main bottleneck when it comes to rendering is the browser main thread getting blocked. This is why we launched CPU charts for synthetic testing over a year ago. Back then it wasn't possible to gather CPU information using real user monitoring (RUM), but the Long Tasks API changes that. Starting today, you can track how CPU impacts your users with SpeedCurve's RUM product, LUX.