SASS vs LESS: which preprocessor should you choose?

SASS vs LESS plays a big role in web design, especially on larger projects where CSS quickly becomes cluttered and difficult to maintain. This is where CSS preprocessors like SASS and LESS come in. They add powerful features such as variables, nesting and mixins, making your CSS smarter and more efficient.

But which one do you choose? SASS and LESS look very similar at first glance, but there are important differences under the hood. In this blog post, we compare both preprocessors and help you determine which one is best for your project.

What are SASS and LESS?

Before we dive into the differences, let's look at what exactly SASS and LESS are and why they are so popular in front-end development.

SASS (Syntactically Awesome Stylesheets).

Developed in 2006, SASS is one of the most advanced and popular CSS preprocessors. It offers two syntax options:

• SCSS (.scss) - Very similar to regular CSS, but adds additional features.

• SASS (.sass) - An indenter-based syntax without braces and semicolons.

SASS allows you to use variables, functions, loops and conditional statements, making it a powerful tool for complex projects. SASS requires a compiler such as Dart SASS to convert the code to standard CSS.

LESS (Leaner Style Sheets).

Introduced in 2009, LESS is known for its simplicity and seamless integration with existing CSS code. It has a syntax very similar to CSS, making it easy to learn. LESS uses a client-side compiler, which means you can even use it directly in the browser without additional tools.

Although LESS is not as advanced as SASS, it still offers powerful features such as variables, mixins and nesting, making it a great choice for developers who want to get started quickly.

Key differences between SASS and LESS

Although SASS and LESS share many similarities, there are key differences that may influence your choice.

Syntax and learning curve.

SASS:

• Two syntax options (.scss and .sass), with .scss being the most commonly used.

• Provides powerful features such as loops and conditional logic.

• Requires a compiler such as Dart SASS to work.

LESS:

• Similar to CSS, making it easier to learn.

• Has less advanced features than SASS.

• Can be used directly in the browser with a JavaScript compiler.

Functionalities and capabilities.

Both preprocessors offer useful features, but SASS goes just a step further in flexibility and complexity.

SASS offers more flexibility, especially with mixins and built-in functions such as loops and conditional statements. LESS, on the other hand, is simpler and immediately usable without much configuration.

Compatibility and ecosystems

SASS:

• Is supported by frameworks such as Foundation and Bulma.

• Works well with modern build tools such as Webpack.

LESS:

• Was used in Bootstrap (until version 3), but is now less popular.

• Less external support than SASS.

When do you choose SASS and when do you choose LESS?

Now that you know what the differences are, the next question is: Which preprocessor is best for your project? This depends on several factors, such as the complexity of your project, your preferences as a developer and the tools you use.

Choose SASS if:

• You are working on a large and complex project.

  SASS provides powerful features such as loops, functions and conditional statements, which is useful for scalable and maintainable code.

• You use modern front-end tools.

  SASS integrates seamlessly with build tools such as Webpack, Gulp and Grunt, making it ideal for an optimized workflow.

• You want a widely supported preprocessor.

  SASS is supported by frameworks such as Foundation and Bulma and has an active community.

Choose LESS if:

• You want to get started quickly without additional configuration.

  LESS can be used directly in the browser without installing a compiler.

• You are using Bootstrap 3 or an older version.

  LESS was the default CSS preprocessor for Bootstrap until version 4, so if you're working with older Bootstrap versions, LESS may be useful. 

• Your project is small and uncluttered.

  For small projects, LESS provides a quick and easy way to improve CSS without the added complexity of SASS.

Practical tips and best practices

Whether you choose SASS or LESS, there are a few general best practices that will help you write efficient and low-maintenance stylesheets.

1. Use a modular structure

Instead of one large CSS file, divide your stylesheets into multiple files:

// Example SASS structure
styles/
│── _variables.scss
│── _mixins.scss
│── _buttons.scss
│── _header.scss
│── main.scss

This will keep your code organized and reusable.

2. Make smart use of variables

Use variables for colors, fonts and spacing to maintain consistency.

// SASS
$primary-color: #3498db;
$font-stack: 'Arial, sans-serif';

body {
  color: $primary-color;
  font-family: $font-stack;
}

// LESS
@primary-color: #3498db;
@font-stack: 'Arial, sans-serif';

body {
  color: @primary-color;
  font-family: @font-stack;
}

3. Use mixins for reusable styles

Mixins prevent code repetition and make your CSS more flexible.

// SASS
@mixin button-style {
  padding: 10px 20px;
  border-radius: 5px;
  background-color: $primary-color;
  color: white;
}

button {
  @include button-style;
}

// LESS
.button-style {
  padding: 10px 20px;
  border-radius: 5px;
  background-color: @primary-color;
  color: white;
}

button {
  .button-style;
}

4. Beware of excessive nesting

Too much nesting can make your CSS unnecessarily complex and affect performance. An example of bad nesting:

// Slecht voorbeeld
header {
  nav {
    ul {
      li {
        a {
          color: $primary-color;
        }
      }
    }
  }
}

Prefer to keep it short and clear:

header nav a {
  color: $primary-color;
}

Which preprocessor is best for your project?

SASS and LESS are both powerful CSS preprocessors that can improve your workflow, but the choice depends on your project and preferences.

• Choose SASS if you have a complex project, use modern tools and need advanced functionality.

• Choose LESS if you are looking for a simpler alternative that works immediately without much configuration.