Pragmatic Guide to Sass 3

29	Debugging Your Sass

Sourcemaps are a feature that allow you to more directly debug your Sass from the browser. Browsers can’t “read” Sass—they need it to be compiled into CSS. This means that when you’re debugging your site locally, you see only the CSS output rather than the Sass that you’ve written. Rather than try to figure out which CSS line corresponds to which Sass line, sourcemaps show the exact Sass line in your code.

Sass sourcemaps are enabled by default when you compile your style sheets. When inspecting an element on the page, you can see the Sass file it came from. In the following case, you can see that the <h1> styles that are being implemented come from the _header.scss partial, on line 5.

Another useful feature is @warn ...