REST API Checker: Test HTTP Requests in Your Browser

Learn how to test REST APIs directly in your browser — send GET, POST, PUT, and DELETE requests, add auth headers, inspect responses, and debug API issues without installing any tools.

Testing APIs shouldn't require Postman, curl, or a terminal

When you're debugging an endpoint, checking if a third-party API is reachable, or quickly validating a response format, reaching for a full API client can feel like overkill. A REST API checker lets you send HTTP requests and inspect responses directly from your browser — no installation, no setup, no saving collections.

It's the fastest way to answer "is this endpoint working?" or "what does this API actually return?"

What a REST API Checker Does

A REST API checker is a lightweight HTTP client. You provide a URL, choose a method, optionally add headers and a request body, and it sends the request and displays the full response — status code, response headers, and body.

This covers the core use cases that come up during API development and integration:

Checking if an endpoint is reachable and returning the expected status code
Inspecting the response body structure before writing parsing code
Testing authentication — does this Bearer token work?
Verifying query parameters — does filtering actually work as documented?
Debugging CORS issues by checking response headers
Quickly checking third-party APIs without switching to a desktop application

HTTP Methods and When to Use Each

Method	Purpose	Has Body?
GET	Retrieve a resource	No
POST	Create a resource or submit data	Yes
PUT	Replace a resource entirely	Yes
PATCH	Partially update a resource	Yes
DELETE	Remove a resource	No (usually)
HEAD	Get headers only, no body	No
OPTIONS	Check supported methods (CORS preflight)	No

Most REST APIs use GET, POST, PUT/PATCH, and DELETE. HEAD and OPTIONS are useful for debugging connectivity and CORS.

How to Use the REST API Checker on sadiqbd.com

Enter the URL — the full endpoint URL including any query parameters.
Select the HTTP method — GET, POST, PUT, PATCH, DELETE, etc.
Add headers — for authenticated APIs, add Authorization: Bearer your-token. For JSON bodies, add Content-Type: application/json.
Enter the request body — for POST/PUT/PATCH requests, paste your JSON payload.
Send the request — the tool fires the request and displays the status code, response headers, and formatted response body.

Real-World Examples

Checking a public API

Testing the JSONPlaceholder API:

GET https://jsonplaceholder.typicode.com/posts/1

Response (200 OK):

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat...",
  "body": "quia et suscipit..."
}

Two seconds to verify the API is up and see the response shape.

Testing an authenticated endpoint

Your internal API requires authentication:

GET https://api.yourapp.com/v1/users/me
Headers:
  Authorization: Bearer eyJhbGc...
  Accept: application/json

If you get 200, the token is valid and working. If you get 401, the token is missing, expired, or malformed. The response body usually contains an error message telling you which.

Sending a POST request

Creating a resource:

POST https://api.yourapp.com/v1/orders
Headers:
  Content-Type: application/json
  Authorization: Bearer eyJhbGc...

Body:
{
  "product_id": 42,
  "quantity": 3,
  "shipping_address": "Dhaka, Bangladesh"
}

The checker returns the response — a 201 Created with the new order object, or a 400 with validation errors explaining what's wrong with the payload.

Debugging CORS

A frontend developer reports their JavaScript fetch call is being blocked. You use the checker to inspect the response headers on the API endpoint:

OPTIONS https://api.example.com/v1/data
Headers:
  Origin: https://yourfrontend.com
  Access-Control-Request-Method: POST

The response headers show whether Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers are present and correctly configured. If they're missing, the CORS issue is server-side.

Understanding HTTP Status Codes

The status code is the first thing to check in any API response.

2xx — Success

200 OK — request succeeded, response body contains result
201 Created — resource was created (POST requests)
204 No Content — success but no body (common for DELETE)

3xx — Redirection

301 Moved Permanently — resource has a new permanent URL
302 Found — temporary redirect
304 Not Modified — cached version is still valid (used with ETags)

4xx — Client errors

400 Bad Request — malformed request, invalid JSON, missing required field
401 Unauthorized — authentication missing or invalid
403 Forbidden — authenticated but not authorised
404 Not Found — resource doesn't exist
422 Unprocessable Entity — request is valid JSON but fails validation
429 Too Many Requests — rate limit exceeded

5xx — Server errors

500 Internal Server Error — something broke on the server
502 Bad Gateway — upstream service failed
503 Service Unavailable — server is down or overloaded
504 Gateway Timeout — upstream service timed out

Tips for API Testing

Always check the Content-Type header. If you're sending JSON, set Content-Type: application/json. Without it, many APIs will reject the request or misparse the body.

Use the response headers to understand caching. Cache-Control, ETag, and Last-Modified headers tell you how the API handles caching. Useful when debugging why a GET is returning stale data.

Check rate limit headers. Many APIs return X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset headers. These tell you how many requests you have left before being throttled.

Test edge cases before writing code. What does the API return for an empty list? For an ID that doesn't exist? For an invalid authentication token? Testing these directly saves debugging time later.

Save your test cases somewhere. The REST API checker is great for one-off tests. For tests you run repeatedly, consider Postman collections, Bruno, or writing integration tests in your codebase.

Frequently Asked Questions

What's the difference between a REST API checker and Postman? Postman is a full-featured API client with workspaces, collections, environments, and test scripting. A REST API checker is lightweight — quick one-off requests with no installation. For quick checks and debugging, the browser tool is faster. For systematic API testing and collaboration, Postman or similar tools are better.

Can I test APIs that require OAuth 2.0? Yes — once you have an access token (from the OAuth flow), add it as a Bearer token in the Authorization header. The checker sends it with the request just like any other header.

What if the API doesn't allow browser requests due to CORS? If the API has restrictive CORS headers, browser-based tools (including this checker) may be blocked — CORS is enforced by the browser, not the tool. In that case, use curl from a terminal or a desktop API client that doesn't run in a browser context.

Can I send binary or multipart form data? Most browser-based REST checkers support JSON and form data. For binary file uploads (multipart/form-data), a desktop tool like Postman or Insomnia handles these more reliably.

Is the REST API Checker free? Yes — completely free, no sign-up needed.

A REST API checker closes the gap between "I need to quickly test this" and "let me open Postman and set up a collection." It's the right tool for quick verification, debugging, and exploration — and being browser-based means it's always one URL away.

Try the REST API Checker free at sadiqbd.com — send HTTP requests and inspect responses instantly.