YAML Builder : A tool for visual layout development of YAML based CSS layouts
csscss : csscss will parse any CSS files you give it and let you know which rulesets have duplicated declarations.
CSS Lint : CSS Lint points out problems with your CSS code. It does basic syntax checking as well as applying a set of rules to the code that look for problemati...
Sizzy : A tool for developing responsive websites crazy-fast.
Open sourced : https://github.com/kitze/sizzy
📦 Parcel : Blazing fast, zero configuration web application bundler
UnCSS is a tool that removes unused CSS from your stylesheets. It works across multiple files and supports Javascript-injected CSS.