Originally developed by Facebook, GraphQL is a powerful query language for APIs that lets developers request exactly the data they need – nothing more, nothing less. In this guide, we’ll break down what GraphQL is, how it works, how it compares to REST, and when it might be the right choice for your project.
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What is GraphQL used for?
GraphQL is a query language – or an interface description language – used to define how two applications talk to each other. It’s also a runtime for APIs that enables clients to request only the data they need. Unlike traditional REST APIs, which return fixed data structures from specific endpoints, GraphQL uses a single endpoint and allows clients to define the shape and amount of data returned. This means more efficient communication between frontend and backend systems.
Created by Facebook in 2012 and open-sourced in 2015, GraphQL is now widely adopted in both startup and enterprise environments. It's especially helpful for building responsive apps with complex data needs.
How does GraphQL work?
GraphQL uses a single endpoint to handle all requests. It relies on a strongly-typed schema that defines the shape of your data and what queries are possible. Clients send structured queries (or mutations, if they’re updating data), and the server responds with just the requested fields.
Key concepts include:
- Schema: A blueprint of the data types and relationships available in your API
- Queries: Used to read or fetch values
- Mutations: Used to create, update, or delete data
- Resolvers: Functions that fetch the actual data for each field in a query
GraphQL is a strongly-typed language, which means it checks that a query is syntactically correct and valid before execution. This makes sure that the query can only refer to types and fields that have been previously defined. To prevent error, it’s also possible to implement variables into the request that can be selected with drop-down menus, search fields, or filters.
Schemas and resolvers
In GraphQL, the schema acts as the blueprint for the API, defining the types of data clients can query and how those types relate to each other. Every GraphQL API needs a schema to outline the structure of queries and mutations. To make this schema functional, resolvers are used. A resolver is the function responsible for fetching the actual data when a specific field in a query is requested. Together, schemas and resolvers enable flexible, precise data access while keeping the backend logic clean and modular.
Queries
Similar to a GET request in REST, a query is used to read or fetch data. Here’s a simple example of how a GraphQL query works in practice:
{
user(id: 1234) {
id
name
isViewerFriend
}
}
The server responds with JSON that mirrors the structure of the original query, making it easy to understand and work with:
{
“data”: {
“user”: {
“id”: “1234”,
“name”: “Stan Smith”,
“isViewerFriend”: true,
},
}
}
This clear and hierarchical data structure makes GraphQL easy to understand and use. Because the response matches the query shape, it reduces the need for multiple requests by only returning the fields explicitly requested.
Mutations
Within a GraphQL setup, an application can create data with ‘Mutations’. These are the equivalent of ‘PUT’ requests in REST, but it has the advantage of increasing the amount of information retrieved per request.
A GraphQL query retrieves all of the requested information from the first node, then moves onto the next node to get the information, and then the next one, and so on until all of the information has been retrieved.
GraphQL vs REST
If you’re weighing up whether to use GraphQL or REST for your next project, it helps to understand the core differences between them. To make the decision easier, we’ve pulled together the main considerations into a handy comparison table below.
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GraphQL |
REST |
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|---|---|---|
| Data efficiency |
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| Flexibility |
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| Ease of use |
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| Performance |
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| Caching |
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