How a GraphQL Request Works

Operations over HTTP

A client usually sends an HTTP POST with a JSON body containing query (the operation text), optional variables and an optional operationName. The server parses the document, validates it against the schema (unknown fields or wrong argument types are rejected before execution), then executes it by calling a resolver for each field. The JSON response has a data key and, when something went wrong, an errors array; a response can contain both (partial success). Queries can also be sent with GET, which helps caching.

A request and its response

The JSON envelope (illustrative data).

// request body: POST /graphql
{
  "query": "query UserCard($id: ID!) { user(id: $id) { name email } }",
  "variables": { "id": "42" },
  "operationName": "UserCard"
}

// response
{
  "data": { "user": { "name": "Asha Verma", "email": "asha@example.com" } }
}

Expect 200 with errors

Many GraphQL servers return HTTP 200 even when the errors array is present, so clients must inspect the body, not just the status code.

त्वरित जाँच: What happens to a query that requests a field not in the schema?

• It fails validation before execution
• The field is returned as null silently
• The server creates the field
• Only the HTTP status changes