# Debugging Transpilation Issues — Babel & SWC

Source: https://www.geekswithgeeks.com/en/babel-swc/bs-debugging

> Tools and techniques to diagnose transformation problems.

## Common issues: when transpilation breaks

Runtime errors after transpilation usually mean: (1) missing polyfill, (2) unsupported syntax, (3) wrong target config, (4) plugin conflict.

## Use browser dev tools with source maps

Enable source maps in build config to debug transpiled code. Errors point to original source, not generated code, making debugging easier.

## Inspect transpiled output

Run Babel/SWC on a single file to see the output and spot problems.

```bash
# Babel
npx babel src/problem.js

# SWC
npx swc src/problem.js

# Save to file for detailed inspection
npx babel src/problem.js -o debug-output.js
```

## Use source maps to trace errors back to source

Enable source maps in Babel/SWC config. Errors in the browser or runtime point to the original source, not the transpiled code.