SourceMap

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

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 header name 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 SourceMap 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

Specification
Source Map specification
# linking-generated-code

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
SourceMap

Legend

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Full support
Full support
See implementation notes.
Requires a vendor prefix or different name for use.
Has more compatibility info.

See also