server side rendering react-helmet "real" css module attach stylesheet with react component using constructable stylesheet dynamic import lazy loading component with its style, to reduce initial load size encapsulate style and component, and lazy load together import a constructed stylesheet and includes/attach in your react component set process.env.ENVIRONMENT to "browser" server side remdering "node.js" make sure your framework has support for import-assertions if you are using gatsby, check out 'gatsby-plugin-import-assertion' for gatsby