A CSS preprocessor is a program that generates CSS from the preprocessor’s own unique syntax. Most preprocessors will add some features like variables, functions, and mixins, that don’t exist in pure CSS. These features make the CSS more readable, easier to maintain, and helps avoid repetitions in the code facilitating more efficient development. Some disadvantages include there can be a knowledge gap in learning CSS preprocessors, the task and time needed to get a team onboard and debugging is more difficult. Three of the most popular and stable CSS preprocessors available today are SASS, LESS, & Stylus. Proficiency in a CSS preprocessor was listed as a desired skill in many of the Web Development job postings I researched.