It is rather a matter of syntax. SASS syntax and SCSS.
Directly from Google’s first result for such a search:
The most commonly used syntax is known as “SCSS” (for “Sassy CSS”) and is a superset of CSS3 syntax. This means that every valid CSS3 stylesheet is also a valid SCSS. SCSS files use the .scss extension. The second, older syntax is known as indented syntax (or simply ".sass").
As for its compatibility with sass-loader in webpack - in the end, the sass loader calls the node-sass library, which itself is built on libsass.
The tools support both forms of syntax, so you can expect to use sass-loader without any problems.
Using sass-loader with old .sass syntax
If you use .sass, you just need to pass the option in the query string when using sass-loader:
loaders: [
{
test: /\.sass$/,
loaders: ["style", "css", "sass?indentedSyntax"]
}
]
sass-loader .scss
.scss , , .
sass-loader: https://github.com/jtangelder/sass-loader