LESS is a dynamic stylesheet language designed by Alexis Sellier. It is influenced by Sass and has influenced the newer "SCSS" syntax of Sass, which adapted its CSS-like block formatting syntax.
LESS is open-source. Its first version was written in Ruby, however in the later versions, use of Ruby has been deprecated and replaced by JavaScript.
The indented syntax of LESS is a nested metalanguage, as valid CSS is valid LESS code with the same semantics. LESS provides the following mechanisms: variables, nesting, mixins, operators and functions; the main difference between other CSS precompilers being that it allows real-time compilation via LESS.js by the browser. LESS can run on the client-side and server-side, or can be compiled into plain CSS.