In SCSS

Comments in SCSS work similarly to comments in other languages like JavaScript. Single-line comments start with //, and go until the end of the line. Nothing in a single-line comment is emitted as CSS; as far as Sass is concerned, they may as well not exist. They’re also called silent comments, because they don’t produce any CSS.

Multi-line comments start with /* and end at the next */. If a multi-line comment is written somewhere that a statement is allowed, it’s compiled to a CSS comment. They’re also called loud comment, by contrast with silent comments. A multi-line comment that’s compiled to CSS may contain interpolation, which will be evaluated before the comment is compiled.

By default, multi-line comments be stripped from the compiled CSS in compressed mode. If a comment begins with /*!, though, it will always be included in the CSS output.

// This comment won't be included in the CSS.

/* But this comment will, except in compressed mode. */

/* It can also contain interpolation:
 * 1 + 1 = #{1 + 1} */

/*! This comment will be included even in compressed mode. */

p /* Multi-line comments can be written anywhere
   * whitespace is allowed. */ .sans {
  font: Helvetica, // So can single-line comments.
        sans-serif;
}

/* But this comment will, except in compressed mode. */
/* It can also contain interpolation:
 * 1 + 1 = 2 */
/*! This comment will be included even in compressed mode. */
p .sans {
  font: Helvetica, sans-serif;
}

In Sass

Comments in the indented syntax work a little differently: they’re indentation-based, just like the rest of the syntax. Like SCSS, silent comments written with // are never emitted as CSS, but unlike SCSS everything indented beneath the opening // is also commented out.

Indented syntax comments that start with /* work with indentation the same way, except that they are compiled to CSS. Because the extend of the comment is based on indentation, the closing */ is optional. Also like SCSS, /* comments can contain interpolation and can start with /*! to avoid being stripped in compressed mode.

Comments can also be used within expressions in the indented syntax. In this case, they have exactly the same syntax as they do in SCSS.

// This comment won't be included in the CSS.
   This is also commented out.

/* But this comment will, except in compressed mode.

/* It can also contain interpolation:
   1 + 1 = #{1 + 1}

/*! This comment will be included even in compressed mode.

p .sans
  font: Helvetica, /* Inline comments must be closed. */ sans-serif

/* But this comment will, except in compressed mode. */
/* It can also contain interpolation:
 * 1 + 1 = 2 */
/*! This comment will be included even in compressed mode. */
p .sans {
  font: Helvetica, sans-serif;
}

Documentation Comments

When writing style libraries using Sass, you can use comments to document the mixins, functions, variables, and placeholder selectors that your library provides, as well as the library itself. These are comments are read by the SassDoc tool, which uses them to generate beautiful documentation. Check out the Susy grid engine’s documentation to see it in action!

Documentation comments are silent comments, written with three slashes (///) directly above the thing you’re documenting. SassDoc parses text in the comments as Markdown, and supports many useful annotations to describe it in detail.

/// Computes an exponent.
///
/// @param {number} $base
///   The number to multiply by itself.
/// @param {integer (unitless)} $exponent
///   The number of `$base`s to multiply together.
/// @return {number} `$base` to the power of `$exponent`.
@function pow($base, $exponent) {
  $result: 1;
  @for $_ from 1 through $exponent {
    $result: $result * $base;
  }
  @return $result;
}

/// Computes an exponent.
///
/// @param {number} $base
///   The number to multiply by itself.
/// @param {integer (unitless)} $exponent
///   The number of `$base`s to multiply together.
/// @return {number} `$base` to the power of `$exponent`.
@function pow($base, $exponent)
  $result: 1
  @for $_ from 1 through $exponent
    $result: $result * $base

  @return $result