https://slack.engineering/chrome-tracing-for-fun-and-profit-a15ec83aa908

You might have used Chrome’s Developer Tools to profile your JavaScript to improve performance or find bottlenecks. DevTools is fantastic, but there’s a lot of potentially useful information that the performance panel doesn’t capture. Enter Chrome Tracing: a tool that’s built into Chrome (and Electron) that can collect a huge variety of detailed performance data. At Slack, we use Chrome Tracing to diagnose complex performance issues, and hopefully after reading this, you’ll be able to as well.

Chrome Tracing consists of two important parts: first, a system for collecting performance-relevant information from the browser itself; and second, a tool for inspecting and analyzing that information. You can try it out for yourself right now by opening chrome://tracing in Chrome. Go ahead and click ‘Record’, select a category (or leave the default ‘Web Developer’ option selected), do something in Chrome, then come back to the tracing tab and click ‘Stop’.