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SourceMap header

files/en-us/web/http/reference/headers/sourcemap/index.md

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The HTTP SourceMap {{Glossary("response header")}} provides the location of a {{Glossary("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.

<table class="properties"> <tbody> <tr> <th scope="row">Header type</th> <td>{{Glossary("Response header")}}</td> </tr> </tbody> </table>

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 SourceMap header

The following response contains an absolute path in the SourceMap header.

http
HTTP/1.1 200 OK
Content-Type: text/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

{{Specifications}}

Browser compatibility

{{Compat}}

See also