Less vs Sass

Because Less has a lightweight feature set, is syntactically similar to CSS and can be run client side with file conversion on a page reload, it is easy to pick up by anyone familiar with CSS & the very basics of JS.

Also, Less has detailed and well-organized documentation, GUI apps that can watch and compile code for you and a huge, active and helpful community.

The LESS syntax is essentially the same as CSS with extensions for dynamic behavior such as variables, mixins, operations and functions.

Variables:

@color: #4D926F;

#header {
  color: @color;
}
h2 {
  color: @color;
}

Mixins:

.rounded-corners (@radius: 5px) {
  -webkit-border-radius: @radius;
  -moz-border-radius: @radius;
  -ms-border-radius: @radius;
  -o-border-radius: @radius;
  border-radius: @radius;
}

#header {
  .rounded-corners;
}
#footer {
  .rounded-corners(10px);
}

Nested Rules:

#header {
  h1 {
    font-size: 26px;
    font-weight: bold;
  }
  p { font-size: 12px;
    a { text-decoration: none;
      &:hover { border-width: 1px }
    }
  }
}

Less contains the base feature-set for a CSS preprocessor:

• Nesting
• Variables
• Basic mathematical operations
• Color functions
• @import
• Basic type functions

Less is one of the most popular preprocessors due to being the easy to learn and its use in Twitter Bootstrap.

Many web developers are familiar with JavaScript and because Less is written in JS, it can be processed client side making the set-up easy.

Apps such as Crunch, SimpLESS, WinLess, Koala, CodeKit, LiveReload or Prepros will watch and compile less.js for you.

IDEs such as VS Code, Visual Studio and WebStorm (and other JetBrains IDEs) support LESS either natively or through plugins.

You are able to declare custom functions with Sass (for example, converting units) which can be easily invoked, even when using shorthand properties. This results in cleaner, more reusable code.

Sass allows you to nest selectors which results in code that is both faster to write and cleaner to read.

For example, this:

.parent 
  color: blue
  .child
    color: yellow

Will compile to this:

.parent {
  color: blue;
}
.parent .child {
  color: yellow;
}

Another big advantage for Sass is the very active community pushing the development forward at a rapid pace. Sass is constantly coming out with bug fixes, and are often the first to come out with improvements.

This is an important factor to keep in mind when picking a preprocessor to invest your time into.

It comes with two possible syntaxes:

• Sass - No parens or semicolons allowed and the nesting is dictated with whitespace.
• SCSS - SCSS syntax is a superset of CSS – which means SCSS can be written as CSS, but has been expanded to include the features of Sass as well.

SCSS is easier to pick up for beginners and Sass has a cleaner syntax. Having both syntaxes means you can pick the one that best suits your coding style.

The mandatory syntax rules for both SCSS and Sass results in a more consistent code. For a more detailed analysis between Sass and SCSS go here. To see a nice comparison of the Sass syntax against CSS and SCSS go here.

Sass simplifies minifying CSS files by offering a one-line command that will output a minified version.

It's very comfortable and easy to write/learn Sass, even for beginners.

Sass can be used with a framework called Compass, which provides additional functions and mixins which can reduce the amount of code you have to write.
For example, Compass will take care of vendor prefixes.

This:

div {
    background-image: -webkit-linear-gradient(#F00, #000);
    background-image: -moz-linear-gradient(#F00, #000);
    background-image: -o-linear-gradient(#F00, #000);
    background-image: linear-gradient(#F00, #000);
   }

Can be written as:

.gradient {
    @include background-image(linear-gradient(#F00, #000));
}

For a full list of features, check out the Compass documentation.

Rather than being limited to editing the outputted CSS file in devtools, with source maps you are able to manipulate the original .scss file.

There is also a C/C++ port of the Sass CSS precompiler called Libsass that decouples Sass from Ruby. It is very fast, portable and easy to build and integrate with a variety of platforms and languages.

The latest implementation of Sass is written in Dart, and compiles to pure JS with no native code or external dependencies, means you no longer need Ruby or libSass.

Since it's written in Ruby, it's easier and faster to use with Ruby apps.