sourceMappingURLenabled

SourceMappingURL is a directive used in generated JavaScript (and, in some contexts, CSS) that links the produced file to its source map. A source map provides a map between the transformed code and the original source, allowing development tools to display original sources, set breakpoints, and produce meaningful stack traces during debugging.

The directive is embedded as a comment at the end of the generated file and references the corresponding source map file. Common forms include // sourceMappingURL=app.js.map or //# sourceMappingURL=app.js.map, though the exact syntax can vary with the language, build tool, or minifier. The referenced URL can be relative or absolute, and some workflows omit the directive in production builds.

Source maps themselves are JSON files that describe how sections of the generated code correspond to sections of the original sources. The standard, known as Source Map Revision 3, includes fields such as version, sources (original file names), names (identifier mappings), mappings (VLQ-encoded position data), and optionally sourcesContent (original source code embedded in the map). This structure enables tools to translate a position in the minified or transpiled code back to the exact location in the original source.

Benefits of using a sourceMappingURL-enabled workflow include improved debugging experience, better error reporting, and visibility into compiled or minified code without exposing source code when maps are kept private. However, publishing source maps can reveal original source content, so teams often configure production builds to omit or protect maps or to restrict access.

In practice, developers enable source maps during development and testing, and configure deployment to control whether maps are distributed publicly.