StyleX

StyleX is a styling library for JavaScript user interfaces. A build-time compiler, run through a Babel or PostCSS plugin or the StyleX CLI, turns style definitions into a static CSS file of atomic class names, and the runtime package is installed from npm in every project that uses it. The docs call StyleX a CSS-in-JS library that is most useful when an application’s UI is authored in JavaScript, and they state that it is framework-agnostic rather than a CSS-in-React solution. Meta Platforms, Inc. maintains the project in a monorepo, and this record covers its core package.