Why there is no "User timing" section in my Chrome DevTools

The User Timing tab was removed from chrome in favour of the "Timings" tab which combines some well known timings, such as LCP, OnLoad Event and custom User Timing API marks/measures.

You need to add ?react_perf to the URL

It's required if you're using React 15 https://reactjs.org/blog/2016/11/16/react-v15.4.0.html#profiling-components-with-chrome-timeline

Not required for React 16 though https://reactjs.org/docs/optimizing-performance.html#profiling-components-with-the-chrome-performance-tab

I was able to make this work by appending ?react_perf to my url. Not sure why this was so difficult to find... hope it works for you.

https://reactjs.org/blog/2016/11/16/react-v15.4.0.html#profiling-components-with-chrome-timeline