Stitches is a CSS-in-JS library and near-zero runtime CSS engine designed to define styles in JavaScript with minimal overhead. It functions as a variant-based styling framework and a tool for server-side rendered CSS, ensuring styles are extracted and rendered on the server to prevent layout shifts during client hydration.
The project distinguishes itself through a structured variants API, allowing for the creation of multiple visual states for components that can be toggled via properties. It implements a system for design system development, focusing on high-performance UI styling and the management of reusable component styles.
The engine covers broad capability areas including atomic CSS generation, token-based theme resolution, and object-to-CSS serialization. It provides specialized styling capabilities for React components and utilizes server-side style injection to prevent flashes of unstyled content.