Source map
File that maps minified/transpiled JS back to the original source. Lets the debugger show your TypeScript/JSX instead of incomprehensible prod bundles.
Format: JSON with VLQ-encoded mapping (compact). Generated automatically by Webpack, Vite, esbuild, tsc. Inline (at file end) or separate .map file. The browser loads them from devtools if a //# sourceMappingURL= comment exists. Security: source maps are often published to production which exposes your source — some teams strip them for prod, others accept it for DX value. CLI tool: source-map-explorer shows bundle size per source file.