From:  Paul Irish <>
Date:  08 Jun 2013 03:35:28 Hong Kong Time

Re: Change sourceMappingURL comment syntax to avoid IE JS conditional compilation issues


To conclude this successful thread....

//@ sourceMappingURL was found to have a conflict with IE whenever it was
found in the page after //@cc_on was interpreted to turn on conditional
compilation in the IE JScript engine. A legacy version of the HTML5 Shiv is
one particular offender here.

*Spec Change*
The //@ sourceMappingURL syntax is defined in the Sourcemap V3 spec:
It was changed there to use //# syntax instead.

//@ sourceURL is also defined in the spec and was made to match the //#
syntax for consistency. For details on what it does, see:

It's used by Ember's minispade, google's concatenate.js, and others.

*Implementation in Browser DevTools = done!*

   - *Safari Inspector* now supports //# for sourceMappingURL and sourceURL
   - *Firebug's* change has
   - *Firefox* is about to
landthe change
for sourceMappingURL. sourceURL ticket
   here .
   - *Chrome* *DevTools* landed the
changefor sourceMappingURL
and sourceURL. It will also warn about use of the
   deprecated //@ syntax.