Less (style sheet language)

Less
Designed byAlexis Sellier
DeveloperAlexis Sellier, Dmitry Fadeyev
First appeared2009 (2009)
Stable release
4.3.0  / 8 April 2025 (8 April 2025)
Typing disciplineDynamic
Implementation languageJavaScript
OSCross-platform
LicenseApache License 2.0
Filename extensions.less
Websitelesscss.org
Influenced by
CSS, Sass
Influenced
Sass, Less Framework, Bootstrap (v3)

Less (Leaner Style Sheets; sometimes stylized as LESS) is a dynamic preprocessor style sheet language that can be compiled into Cascading Style Sheets (CSS) and run on the client side or server side. Designed by Alexis Sellier, Less is influenced by Sass and has influenced the newer "SCSS" syntax of Sass, which adapted its CSS-like block formatting syntax. Less is an open source project. 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 Less and other CSS precompilers is that Less allows real-time compilation via less.js by the browser.