postcss-scss is a PostCSS syntax parser that allows developers to write SCSS-style syntax in their CSS files. It enables the use of SCSS features such as nesting, variables, and mixins while still leveraging the powerful PostCSS ecosystem for processing and transforming stylesheets. This package is particularly useful for those who want to maintain the SCSS syntax while benefiting from PostCSS plugins for additional functionality.

While postcss-scss is a great tool, there are several alternatives that cater to different needs in the CSS processing landscape:

• postcss-cssnext is a PostCSS plugin that allows developers to use the latest CSS features without worrying about browser compatibility. It automatically transforms modern CSS syntax into a format that works across all browsers. If you want to write cutting-edge CSS while ensuring compatibility, postcss-cssnext is an excellent choice.
• postcss-less is a PostCSS parser for LESS syntax. It allows developers to write styles using LESS features while still taking advantage of PostCSS's powerful plugin ecosystem. If you prefer using LESS but want to integrate with PostCSS, this package is ideal.
• postcss-modules enables CSS Modules in your project, allowing for scoped CSS and avoiding global namespace conflicts. This is particularly useful for larger projects where modularity and maintainability are crucial. If you want to leverage the benefits of CSS Modules while using PostCSS, this is a great option.
• postcss-nested is a plugin that allows you to use nested rules in your CSS, similar to SCSS. It enables a more organized and readable structure for your stylesheets. If you like the nesting feature of SCSS but want to stick with standard CSS, postcss-nested is a suitable alternative.
• postcss-sass is another PostCSS plugin that allows you to use SASS syntax in your stylesheets. It provides similar functionality to postcss-scss but focuses on SASS-specific features. If you prefer SASS syntax and want to use PostCSS, this package is worth considering.

To compare these packages and see how they stack up against each other, check out the following link: Comparing postcss-cssnext vs postcss-less vs postcss-modules vs postcss-nested vs postcss-sass vs postcss-scss.