WPGraphQL is an open-source WordPress plugin that adds a fully featured GraphQL API to any WordPress installation. It transforms WordPress from a self-contained CMS into a content platform queryable by any GraphQL client — a Next.js front end, a mobile app, a Hugo build process, or any other consumer capable of making HTTP requests. The REST API built into WordPress core works, but GraphQL solves problems the REST API does not handle elegantly: over-fetching unnecessary fields, under-fetching requiring multiple round-trips, and querying relational data efficiently.