💡 Ever wonder how we make bundling faster in @Expo CLI / Metro? The trick is to measure and examine command times, aka "profiling". Here's how to do it: 1️⃣ First disable multi-threaded bundling by passing `--max-workers 1` (or zero) to `expo export` or `expo start`. This is extremely useful for debugging Babel and the transformer as everything will run on the main thread. 2️⃣ Next run Expo CLI directly with Node inspection enabled. This command will perform a single iOS JS build on the main thread: node --inspect-brk ./node_modules/.bin/expo export -p ios --max-workers 1 3️⃣ Then go to Chrome and visit: chrome://inspect/#devices Clicking "inspect" under the "Target" section will attach Chrome Dev Tools to Expo CLI. 4️⃣ From here, open the [performance] tab and press the record button, then wait until the console logs indicate that bundling is complete, finally stop the recording. 5️⃣ Now the fun begins! We now have a list of the most expensive tasks, which we can examine for abnormalities. Sort by "Total Time" and go down the list looking for areas to improve bundling. In the above example, we can see that reading the tsconfig ranks pretty high. All I have to do from here is investigate that method and see if there are ways to speed it up or reduce the amount of times we call it. Real world example ↓