Relay

Relay is a highly opinionated JavaScript framework for building data-driven React applications with GraphQL, developed and maintained by Meta (formerly Facebook). It was designed to power some of the largest React applications in the world, including Facebook.com, Instagram, and Workplace, and is built to handle the unique challenges of managing complex data requirements in large-scale applications where hundreds of components may need different slices of data from a shared GraphQL API. Unlike other GraphQL clients like Apollo Client or urql, Relay takes a fundamentally different approach to data fetching: instead of top-level queries, Relay uses a fragment-based architecture called colocation, where data requirements are declared at the component level using GraphQL fragments and the framework automatically composes these fragments into optimized queries. This means each component specifies exactly what data it needs via a fragment, and Relay handles the complex task of combining fragments from an entire component tree into a single efficient network request. Key features include: the compiler (relay-compiler) that validates fragments, generates optimized query artifacts, and detects unused fields at build time, data masking (a component can only access the fields it explicitly requests in its fragment, preventing implicit dependencies), automatic pagination via connection-based pagination (using the @connection and loadMore patterns), mutations with optimistic updates and automatic store updates, subscriptions for real-time data via GraphQL Subscriptions, client-side state management via the Relay store with @updaters, directives like @arguments and @argumentDefinitions for parameterized fragments, the @required action for handling nullable fields, and Suspense integration for declarative data loading. As of 2026, Relay has over 18,000 GitHub stars.