Less CSS is a dynamic stylesheet language that extends the capabilities of CSS, allowing developers to write cleaner, more modular, and reusable stylesheets with features like variables, mixins, and nested rules.

SCSS is a preprocessor scripting language that extends the capabilities of CSS by adding features such as variables, nesting, and mixins. It allows developers to write more efficient and maintainable CSS code, and helps to streamline the development process by reducing repetition and increasing reusability.

ESLint is a linter for JavaScript that analyzes code to detect and report on potential problems and errors, as well as enforce consistent code style and best practices, helping developers to write cleaner, more maintainable code.

Gulp.js is an old but popular site building tool that automates various repetitive development tasks in web development, such as compiling Sass, minifying JavaScript, and optimizing images.

PostCSS is a popular open-source tool that enables web developers to transform CSS styles with JavaScript plugins. It allows for efficient processing of CSS styles, from applying vendor prefixes to improving browser compatibility, ultimately resulting in cleaner, faster, and more maintainable code.