GraphQL Query Language

GraphQL is a query language for APIs and a runtime for fulfilling those queries with existing data, developed internally by Facebook (now Meta) in 2012 and open sourced in 2015. Unlike traditional REST APIs that require multiple round trips to different endpoints, GraphQL provides a complete and understandable description of the data in an API through a single endpoint, giving clients the power to ask for exactly what they need and nothing more. The type system enables powerful developer tools including type checking, automatic documentation, intelligent code completion, and schema introspection. Queries return predictable results organized in the same shape as the request, while the built-in validation ensures that only valid queries are executed. GraphQL supports three operation types: queries for reading data, mutations for writing data with automatic cache updates, and subscriptions for real-time data streaming via WebSocket. The GraphQL specification is maintained by the GraphQL Foundation under the Linux Foundation, ensuring vendor-neutral governance. Major companies including Facebook, Instagram, GitHub, Shopify, Twitter (X), Airbnb, PayPal, Atlassian, Coursera, and Yelp use GraphQL in production at massive scale. Popular server implementations include Apollo Server, GraphQL Yoga, and Mercurius, while client libraries like Apollo Client, Relay, and urql provide caching, pagination, and optimistic UI updates for web and mobile applications.