How APIs Use JSON: REST, GraphQL, and WebSocket Data Formats
A developer-focused guide to how modern APIs use JSON for request/response payloads, error handling, pagination, and real-time communication.
JSON in REST APIs
REST APIs use JSON as the primary data format for both requests and responses. A typical REST response includes status, data, and metadata. JSON's lightweight syntax and native browser support make it the default choice for RESTful services. Most major web APIs — from GitHub to Stripe to Google — use JSON as their primary data format.
JSON in GraphQL APIs
GraphQL uses a JSON-like query syntax and always returns JSON responses. Unlike REST, GraphQL lets clients specify exactly which fields they need, reducing over-fetching and under-fetching of data. GraphQL responses follow a standard envelope pattern with data and errors fields, making error handling predictable and consistent across all queries and mutations.
JSON API Error Handling Patterns
Standardized error responses help client applications handle failures gracefully. The JSON:API specification defines a standard error format with title, detail, status, and source fields. Many APIs include an errors array in their JSON response body with a code, message, and optional details for each error, making debugging straightforward for client developers.
JSON Pagination Strategies for APIs
APIs serving large datasets implement pagination to avoid overwhelming clients. Common JSON pagination patterns include cursor-based (using a next_cursor field), offset-based (page/limit parameters), and page-based (page_number/page_size). Each approach has trade-offs for consistency, performance, and ease of client implementation.
Real-Time JSON with WebSockets
WebSocket APIs use JSON frames for real-time bidirectional communication. JSON's self-describing nature makes it ideal for messaging protocols where different message types carry different data structures. Common patterns include a type field to dispatch messages, a data payload for the actual content, and optional metadata fields for timestamps and correlation IDs.
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