Understanding Sass Comment Syntax and CSS Output

Sass, or Syntactically Awesome Stylesheets, provides developers with a robust and concise way to write their CSS. Sass offers several features not available in standard CSS, including variables, nesting, mixins, and, importantly, different types of comments.

In programming, comments are vital to explain what code does, but they're generally not needed in the final output. Sass is unique in offering two types of comments - those that make it to the final CSS output and those that don't.

The standard comment syntax in Sass, similar to CSS and many other languages, uses /* */. However, these comments do not appear in the compiled CSS output when Sass is configured for production use because they're stripped out to minimize file size.

If you want Sass to retain comments in the generated CSS output, you use the /*! */ syntax. These are called "loud comments," and the exclamation mark (!) signals to Sass that these are essential and should remain in the final CSS output.

Here's an example:

/*! This comment will appear in the compiled CSS output */
body {
 margin: 0;
 padding: 0;
}

In the CSS output, you will find:

/*! This comment will appear in the compiled CSS output */
body {
 margin: 0;
 padding: 0;
}

Meanwhile, any comments written with // or /* */ syntax will be removed during compilation.

This feature is particularly useful when you want to include metadata, licensing information, or any essential comments in your CSS file that need to be seen by those dealing with your compiled code.

As a best practice, be judicious in your use of "loud comments". Remember that any text you include adds to your final file's size and loading time. Always focus on keeping your comments concise, clear, and useful, whether you're coding in Sass or any other language.