style9

style9 is a compile-time CSS-in-JS library inspired by Facebook's Stylex, extracting atomic CSS strings during build with near-zero runtime overhead. Version 0.18.2 ships TypeScript types and supports Webpack, Rollup, Next.js, Gatsby, and Vite via dedicated plugins. It uses a style.create() pattern similar to styled-components but outputs deterministic class names and minimal runtime (just a single function that maps conditions to pre-computed class strings). Unlike runtime-heavy alternatives, style9 shifts all style computation to build time, making it suitable for performance-critical applications. The library is framework-agnostic and actively maintained on GitHub.