React Scan by Aiden Bai automatically detects performance issues in React apps. From the website:

Previously, existing tools required lots of code change, lacked simple visual cues, and didn’t have a simple, portable API

Instead, React Scan:

• Requires no code changes – just drop it in
• Highlights exactly the components you need to optimize
• Available via script tag, npm, CLI, you name it!

React Scan will soon show what props caused a component to render as well:

And allow for recording and replying renders!

Previously: Bippy and React Fibers.