SourceMap header

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.

See full compatibility

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

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

Specification
Source map format specification # sec-linking-http-header

Browser compatibility

	desktop					mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS
`SourceMap`	Chrome – Full support Chrome 18 (Release date: 2012-03-28) prefix prefix Implemented with the vendor prefix: X- Chrome – Full support Chrome 18 (Release date: 2012-03-28) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	Edge – Full support Edge 79 (Release date: 2020-01-15) prefix prefix Implemented with the vendor prefix: X- Edge – Full support Edge 79 (Release date: 2020-01-15) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	Firefox – Full support Firefox 27 (Release date: 2014-02-04) prefix prefix Implemented with the vendor prefix: X- Firefox – Full support Firefox 55 (Release date: 2017-08-08) footnote Full support	Opera – Full support Opera 15 (Release date: 2013-07-02) prefix prefix Implemented with the vendor prefix: X- Opera – Full support Opera 15 (Release date: 2013-07-02) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	Safari – Full support Safari 6 (Release date: 2012-07-25) prefix prefix Implemented with the vendor prefix: X- Safari – Full support Safari 7 (Release date: 2013-10-22) footnote Full support	Chrome Android – Full support Chrome Android 18 (Release date: 2012-06-27) prefix prefix Implemented with the vendor prefix: X- Chrome Android – Full support Chrome Android 18 (Release date: 2012-06-27) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	Firefox for Android – Full support Firefox for Android 27 (Release date: 2014-02-04) prefix prefix Implemented with the vendor prefix: X- Firefox for Android – Full support Firefox for Android 55 (Release date: 2017-08-08) footnote Full support	Opera Android – Full support Opera Android 14 (Release date: 2013-05-21) prefix prefix Implemented with the vendor prefix: X- Opera Android – Full support Opera Android 14 (Release date: 2013-05-21) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	Safari on iOS – Full support Safari on iOS 6 (Release date: 2012-09-10) prefix prefix Implemented with the vendor prefix: X- Safari on iOS – Full support Safari on iOS 7 (Release date: 2013-09-18) footnote Full support	Samsung Internet – Full support Samsung Internet 1 (Release date: 2013-04-27) prefix prefix Implemented with the vendor prefix: X- Samsung Internet – Full support Samsung Internet 1 (Release date: 2013-04-27) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	WebView Android – Full support WebView Android 4.4 (Release date: 2013-12-09) prefix prefix Implemented with the vendor prefix: X- WebView Android – Full support WebView Android 4.4 (Release date: 2013-12-09) footnote footnote Not supported for ECMAScript Modules (`<script type="module">`). See bug 40854862.	WebView on iOS – Full support WebView on iOS 6 (Release date: 2012-09-10) prefix prefix Implemented with the vendor prefix: X- WebView on iOS – Full support WebView on iOS 7 (Release date: 2013-09-18) footnote Full support

Tip: you can click/tap on a cell for more information.

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