SourceMap
The HTTP SourceMap response header provides the location of a source map for the resource.
The HTTP SourceMap header has precedence over a source annotation (sourceMappingURL=path-to-map.js.map), and if both are present, the header URL is used to resolve the source map file.
| Header type | Response header |
|---|---|
| Forbidden request header | No |
Syntax
http
SourceMap: <url>
X-SourceMap: <url> (deprecated)
Directives
<url>-
A relative (to the request URL) or absolute URL pointing to a source map file.
Examples
Linking to a source map using the <code>SourceMap</code> header
The following response contains an absolute path in the SourceMap header.
http
HTTP/1.1 200 OK
Content-Type: application/javascript
SourceMap: /path/to/file.js.map
<optimized-javascript>
Developer tools use the source map to reconstruct the original source from the optimized JavaScript returned in the response, allowing developers to debug the original code rather than the format that has been optimized for sending.
Specifications
Browser compatibility
See also
- Source map
- Firefox Developer Tools: using a source map
- What are source maps? on web.dev (2023)