Difference Between @import and @use in Sass

Sass (Syntactically Awesome Style Sheets) provides two directives for including styles from other files: @import and @use. While both serve the purpose of importing styles, they have significant differences in functionality, organization, and best practices. Below, we will explore these differences in detail.

1. Purpose and Functionality

The @import directive is used to include the contents of one Sass file into another. It allows you to import styles, variables, mixins, and functions from other files. However, it has some limitations, such as potential duplication of styles and a lack of namespace management.

On the other hand, the @use directive is a more modern approach introduced in Sass modules. It loads a Sass file and makes its variables, mixins, and functions available in the current stylesheet. The @use directive automatically prevents duplication and provides better organization through namespacing.

2. Namespacing

One of the key differences between @import and @use is how they handle namespacing. When you use @import, all variables, mixins, and functions are available globally, which can lead to naming conflicts.

In contrast, @use automatically namespaces the imported file, meaning you must prefix the variables, mixins, and functions with the name of the file (or a custom namespace) to avoid conflicts.

/* _colors.scss */
$primary-color: #3498db;

/* styles.scss using @import */
@import 'colors'; /* Imports without namespace */
.button {
    background-color: $primary-color; /* Direct access */
}

/* styles.scss using @use */
@use 'colors'; /* Imports with namespace */
.button {
    background-color: colors.$primary-color; /* Access with namespace */
}
    

3. Avoiding Duplication

With @import, if you import the same file multiple times, Sass will include it each time, which can lead to duplication in the compiled CSS. This is particularly problematic in larger projects.

In contrast, @use ensures that a file is only loaded once, regardless of how many times it is referenced. This helps maintain a clean and efficient output.

/* _variables.scss */
$primary-color: #3498db;

/* styles.scss using @import */
@import 'variables'; /* First import */
@import 'variables'; /* Second import, may cause duplication */

/* styles.scss using @use */
@use 'variables'; /* Only loaded once */
.button {
    background-color: variables.$primary-color; /* Access with namespace */
}
    

4. Loading Stylesheets

When using @import, you can import both Sass and CSS files. However, @use is specifically designed for Sass files and does not support importing CSS files directly.

@import 'styles.css'; /* Valid with @import */
@use 'styles.css'; /* Invalid with @use */
    

5. Best Practices

As of now, it is recommended to use @use over @import for new projects due to its advantages in organization, namespacing, and avoiding duplication. The @import directive is still supported for backward compatibility, but it is considered less efficient and more prone to issues.

6. Conclusion

In summary, the main differences between @import and @use in Sass lie in their functionality, namespacing, handling of duplication, and best practices. While @import is a traditional method for including styles, @use offers a more modern and efficient approach to managing stylesheets. Adopting @use in your Sass projects can lead to cleaner, more maintainable code.