How are Less and Sass implemented?

Less is implemented through parsing and transpiling at runtime using JavaScript. When a Less file is loaded into the browser, the JavaScript code parses the file and converts it into regular CSS code, which is then applied to the page.

There are two ways to implement Sass: Ruby Sass and LibSass.

1. Ruby Sass, written in Ruby, is the original implementation of Sass. When a Sass file is loaded into the browser, the Ruby code parses the file and converts it into CSS code, which is then applied to the page.
2. LibSass is a standalone library written in C/C++. It has a faster compilation speed compared to Ruby Sass and is easier to integrate into other build tools. Many front-end build tools like Webpack and Gulp use LibSass to compile Sass files.