Modern web apps suffer from main thread congestion, causing jank and poor user experience. Current profiling tools are either too heavy or don't focus specifically on the main thread.
Build a browser extension or standalone tool that visually maps main thread activity, highlighting expensive operations and suggesting optimizations.
Freelance developers and tech leads would pay for this to deliver smoother experiences and reduce debugging time.
Start with a Chrome extension that overlays a simple performance heatmap during development.
The biggest risk is competing with browser dev tools that may eventually incorporate similar features.