JSON:API is a specification for building APIs that use JSON. It's not just another way to format JSON—it's a complete standard that defines how clients and servers should communicate, how to structure requests and responses, and how to handle relationships, pagination, filtering, and more.

Think of JSON:API as a set of rules that makes APIs more consistent, predictable, and easier to work with. Instead of every API having its own unique structure, JSON:API provides a common pattern that developers can learn once and use everywhere. For practical examples of working with APIs, see our Working with JSON APIs guide.

Key Point: JSON:API is a specification, not a library or framework. It defines the rules for how JSON should be structured in API communication. Learn more at jsonapi.org.

Why JSON:API Was Created

Before JSON:API, every REST API had its own unique way of structuring JSON responses. This led to several problems:

•

Inconsistency: Every API had different patterns for errors, pagination, relationships

•

Learning Curve: Developers had to learn each API's unique structure

•

Over-fetching/Under-fetching: No standard way to request related data efficiently

•

No Tooling: Hard to build generic API clients and tools

JSON:API solves these problems by providing a standard that's detailed enough to be useful but flexible enough for most use cases. Learn more about JSON:API format specification.

Basic JSON:API Response Structure

Every JSON:API response follows a consistent structure. Here's a simple example:

Simple Resource Response

{
  "data": {
    "type": "articles",
    "id": "1",
    "attributes": {
      "title": "JSON:API Tutorial",
      "content": "Learn about JSON:API...",
      "published": true
    }
  }
}

Key elements: data contains the resource,type identifies the resource type,id is the unique identifier,attributes holds the actual data.

Relationships in JSON:API

One of JSON:API's most powerful features is how it handles relationships between resources. You can include related data or just reference it.

Resource with Relationships

{
  "data": {
    "type": "articles",
    "id": "1",
    "attributes": {
      "title": "Understanding JSON:API"
    },
    "relationships": {
      "author": {
        "data": { "type": "people", "id": "9" }
      },
      "comments": {
        "data": [
          { "type": "comments", "id": "5" },
          { "type": "comments", "id": "12" }
        ]
      }
    }
  }
}

The relationships key defines connections to other resources.

Including Related Resources (Compound Documents)

{
  "data": {
    "type": "articles",
    "id": "1",
    "attributes": {
      "title": "Understanding JSON:API"
    },
    "relationships": {
      "author": {
        "data": { "type": "people", "id": "9" }
      }
    }
  },
  "included": [
    {
      "type": "people",
      "id": "9",
      "attributes": {
        "name": "Dan Gebhardt",
        "twitter": "@dgeb"
      }
    }
  ]
}

The included array contains related resources to avoid additional requests.

Collections and Arrays

When returning multiple resources, the data key contains an array:

Collection Response

{
  "data": [
    {
      "type": "articles",
      "id": "1",
      "attributes": {
        "title": "First Article"
      }
    },
    {
      "type": "articles",
      "id": "2",
      "attributes": {
        "title": "Second Article"
      }
    }
  ],
  "meta": {
    "total": 42
  }
}

The meta object can contain additional information like total count.

Pagination in JSON:API

JSON:API provides standard links for pagination:

Paginated Response

{
  "data": [
    // ... array of resources
  ],
  "links": {
    "self": "https://api.example.com/articles?page[number]=2",
    "first": "https://api.example.com/articles?page[number]=1",
    "prev": "https://api.example.com/articles?page[number]=1",
    "next": "https://api.example.com/articles?page[number]=3",
    "last": "https://api.example.com/articles?page[number]=10"
  },
  "meta": {
    "total-pages": 10,
    "total-items": 200
  }
}

Clients can easily navigate through pages using the provided links.

Error Responses

JSON:API has a standard format for errors with detailed information:

Error Response Example

{
  "errors": [
    {
      "status": "422",
      "title": "Invalid Attribute",
      "detail": "Title must be at least 3 characters long",
      "source": {
        "pointer": "/data/attributes/title"
      }
    },
    {
      "status": "422",
      "title": "Invalid Attribute",
      "detail": "Email has already been taken",
      "source": {
        "pointer": "/data/attributes/email"
      }
    }
  ]
}

Each error includes status, title, detail, and can point to the specific field that caused it.

Key Features of JSON:API

1. Sparse Fieldsets

Request only the fields you need:

GET /articles?fields[articles]=title,body

2. Filtering

Filter resources with query parameters:

GET /articles?filter[published]=true

3. Sorting

Sort by one or more fields:

GET /articles?sort=-created,title

The minus sign (-) indicates descending order.

4. Including Related Resources

Fetch related data in a single request:

GET /articles/1?include=author,comments

When to Use JSON:API

✅ Good Use Cases

•Complex data with many relationships
•Public APIs used by many clients
•Need for consistency across endpoints
•Building reusable API clients
•Need advanced filtering/pagination

❌ May Not Be Ideal For

•Very simple APIs with flat data
•Microservices with unique needs
•Performance-critical scenarios (overhead)
•When team isn't familiar with spec
•Real-time streaming data

JSON:API vs Traditional REST APIs

Aspect	Traditional REST	JSON:API
Structure	Varies by API	Standardized format
Relationships	Nested or separate requests	Built-in with `include`
Pagination	Custom implementation	Standard links pattern
Errors	Varies widely	Structured error objects
Flexibility	Completely flexible	Structured but extensible
Learning Curve	Learn each API	Learn once, use everywhere

JSON:API Libraries and Tools

Many libraries exist to help you implement JSON:API in various languages:

Find more implementations at jsonapi.org/implementations.

Helpful Tools for Working with JSON:API

JSON Formatter

Format and beautify JSON:API responses for better readability

JSON Validator

Validate JSON:API response structure and syntax

JSON Examples

Learn JSON structure with practical examples

Working with JSON APIs

Practical guide to building and consuming JSON APIs

Learn More About JSON:API

Official JSON:API Site

Complete specification and documentation

JSON:API Format Specification

Detailed technical specification

JSON:API Implementations

Libraries for various programming languages

JSON:API Examples

Example requests and responses

Summary

JSON:API is a powerful specification for building consistent, predictable APIs with JSON. It solves common problems like relationship handling, pagination, and error formatting by providing a standard structure.

•Standardized structure for requests and responses
•Built-in support for relationships and compound documents
•Consistent patterns for pagination, filtering, and sorting
•Structured error handling with detailed information
•Extensive ecosystem of libraries and tools

Next Steps: Ready to build or consume JSON APIs? Check our practical guide to working with JSON APIs with code examples in multiple languages.

What is JSON:API? Complete Guide to the Specification