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REST API Tester Online

Test REST API endpoints with custom headers and JSON bodies.

About This Tool

Test REST API endpoints with custom headers and JSON bodies. This tool runs entirely in your browser — no data is ever sent to a server. Free to use, no account required.

What the JSON API Tester Does

The API tester lets you send HTTP requests and inspect JSON responses directly in your browser, without installing a dedicated API client.

Making HTTP Requests

Configure the HTTP method (GET, POST, PUT, PATCH, DELETE), enter the URL, add request headers, and write a JSON request body. Click Send and the tool makes the actual HTTP request from your browser.

Inspecting JSON Responses

The response body is automatically parsed and syntax-highlighted for easy reading. Status code, response time, and response headers are displayed alongside the formatted JSON body.

When to Use the JSON API Tester

The API tester is ideal for quick exploration and debugging without the overhead of a full API client installation.

Quick API Exploration

Test a public API endpoint immediately without installing Postman, Insomnia, or another dedicated API client. The tool is available instantly in your browser with no setup required.

Debugging JSON Payloads

Send a JSON request body and immediately see the server response. Iterate quickly on the request structure, headers, or endpoint URL to debug API integration issues.

Frequently Asked Questions

What is a JSON API tester?

A JSON API tester is a browser-based HTTP client for sending requests to REST APIs and viewing the JSON responses. Enter the URL, select the HTTP method, add headers, and write a JSON request body if needed. The tool sends the request and displays the response body, status code, and headers — like a simplified Postman directly in your browser.

Can I send POST requests with a JSON body?

Yes. Select the POST method, enter your endpoint URL, add the Content-Type: application/json header, and paste or write your JSON request body. The tool sends the JSON body and displays the server's response. You can also test PUT and PATCH requests the same way.

Does the API tester support authentication?

Yes. Add an Authorization header with your token (e.g., Bearer your-token-here) or use Basic auth. API keys can be added as headers or query parameters. The tool sends whatever headers you specify, so any HTTP-based authentication scheme works.

Are there CORS restrictions when testing APIs?

Yes. Browser-based API clients are subject to CORS restrictions. If an API does not include the appropriate Access-Control-Allow-Origin response header, the browser will block the request. Public APIs and APIs you control work without issues. For CORS-restricted APIs, test from a server-side tool instead.

REST API Testing with JSON

Testing REST APIs requires sending HTTP requests with JSON payloads and inspecting JSON responses. Understanding request/response structure is essential for API development and integration.

HTTP Methods and JSON Body

Method	Request Body	Purpose	Example Path
GET	No body	Retrieve data	/api/users/1
POST	JSON body	Create resource	/api/users
PUT	JSON body	Replace resource	/api/users/1
PATCH	JSON body	Partial update	/api/users/1
DELETE	No body	Delete resource	/api/users/1

Example API Request and Response

// POST /api/users
// Request Headers
Content-Type: application/json
Authorization: Bearer eyJhbGc...

// Request Body
{
  "name": "Alice",
  "email": "alice@example.com",
  "role": "user"
}

// Response: 201 Created
{
  "id": "uuid-123",
  "name": "Alice",
  "email": "alice@example.com",
  "role": "user",
  "createdAt": "2024-01-15T10:30:00Z"
}

Common REST API Status Codes

Status Code	Meaning
200 OK	Request succeeded
201 Created	Resource created successfully
400 Bad Request	Invalid JSON or missing required fields
401 Unauthorized	Missing or invalid authentication token
403 Forbidden	Authenticated but insufficient permissions
404 Not Found	Resource does not exist
422 Unprocessable	Validation errors in request body
500 Server Error	Internal server error — check server logs

Explore more tools: All JSON Tools | Validator | Pretty Print | JSON Diff

Testing REST APIs with JSON: Common Patterns

RESTful APIs follow a consistent pattern: each HTTP method maps to a CRUD operation, and the JSON request/response structure is predictable. The table below covers the full set of operations for a typical /users resource.

Operation	Method	Path	Request Body	Expected Response
Create	POST	/users	{"name":"Alice","email":"alice@example.com"}	201 + created object
Read all	GET	/users	None	200 + array of users
Read one	GET	/users/1	None	200 + single user
Update	PUT	/users/1	{"name":"Alice Updated"}	200 + updated object
Partial update	PATCH	/users/1	{"email":"new@example.com"}	200 + updated object
Delete	DELETE	/users/1	None	204 No Content

Interpreting HTTP Response Codes

HTTP status codes are grouped by their first digit: 2xx means success, 4xx means a client error (your request is wrong), and 5xx means a server error (the server is broken). Knowing the exact code immediately tells you where to look when debugging.

Code	Meaning	Common in APIs
200 OK	Success	GET, PUT, PATCH
201 Created	Resource created	POST
204 No Content	Success, no body	DELETE
400 Bad Request	Invalid JSON or params	All
401 Unauthorized	Missing/invalid auth	All
403 Forbidden	Valid auth, no permission	All
404 Not Found	Resource doesn't exist	GET, PUT, DELETE
422 Unprocessable	Valid JSON, failed validation	POST, PUT
429 Too Many Requests	Rate limited	All
500 Internal Server Error	Server bug	All