What is Source Map?
A file mapping minified or transpiled production code back to original source, enabling readable stack traces and debugging.
Definition
A source map (.map file) encodes, via base64 VLQ mappings, how each position in generated code corresponds to the original TypeScript, JSX, or Sass a developer wrote. Browsers' DevTools consume the //# sourceMappingURL comment to show original files with working breakpoints; error-monitoring services like Sentry ingest maps to unminify production stack traces. Bundlers emit several fidelity levels—full, cheap, inline—trading build speed against debugging quality. Because maps can expose proprietary source, teams commonly upload them privately to their error tracker while withholding them from public URLs, or serve them only to authenticated origins.