All 15 GraphQL questions
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Node.js › GraphQL

What is GraphQL, and how does it differ from a traditional REST API in terms of how clients request data?

Beginner

Answer

GraphQL is a query language and runtime for APIs where the client specifies exactly which fields it needs in a single request, and the server returns precisely that shape of data -- unlike REST, where each endpoint returns a fixed data shape (often requiring multiple requests to different endpoints to gather related data, or over-fetching unnecessary fields from a single endpoint), GraphQL exposes a single endpoint with a strongly-typed schema, letting clients compose exactly the query they need.
# GraphQL query: client specifies exactly the fields it wants
query {
  user(id: "123") {
    name
    email
    orders { id total }
  }
}

# A single request returns exactly this nested shape, no more, no less
Real-world example A mobile app with limited bandwidth switches a screen from three separate REST API calls (user profile, orders, and preferences) to a single GraphQL query requesting exactly the fields needed for that screen, reducing both the number of round trips and the amount of unused data transferred.

Common follow-ups: What's the specific problem of 'over-fetching' and 'under-fetching' in REST that GraphQL is designed to solve?;Does GraphQL replace REST entirely, or are there scenarios where REST is still the better choice?

RESTful API Design with Express;HTTP & Web Servers
All 15 GraphQL questions