REST API Tester
A free browser-based HTTP client to test REST APIs, send HTTP requests (GET, POST, PUT, DELETE, PATCH), bypass CORS, and inspect response payloads.
A free browser-based HTTP client to test REST APIs, send HTTP requests (GET, POST, PUT, DELETE, PATCH), bypass CORS, and inspect response payloads.
This developer tool is built with a privacy-first mindset. All transformations, formatting, and operations execute entirely in your local browser sandbox without transmitting sensitive tokens, keys, or code to external servers.
REST - Representational State Transfer - is an architectural style that defines how systems communicate over HTTP. It's not a protocol or a library. It's a set of constraints: stateless communication, uniform resource URLs, and standard HTTP verbs (GET, POST, PUT, DELETE, PATCH) to express intent. When an architecture follows these constraints, we call it RESTful.
In my 15+ years of building distributed systems, REST APIs have been the backbone of virtually every product I've shipped — from internal microservices to third-party developer platforms. The beauty of REST is its simplicity: a URL identifies a resource, and the HTTP method tells the server what to do with it. GET /users/42 - fetches a user. DELETE /users/42 - removes them. No magic, no ceremony.
REST APIs power nearly everything you interact with online - payment gateways, social feeds, weather apps, authentication systems. If you're building or consuming web services, understanding REST isn't optional. It's foundational.
This REST API Tester is a browser-native HTTP client built for developers who need to debug, test, and inspect APIs without spinning up Postman or writing a curl command. You get the full picture of every request: status code, response time, response headers, and a syntax-highlighted JSON body — all without leaving your browser tab.
It supports all five core HTTP methods: GET, POST, PUT, DELETE, and PATCH. You can add custom request headers (Authorization, Content-Type, X-API-Key - whatever your API needs), append query parameters, and craft JSON request bodies for POST and PUT calls. The response panel gives you the raw body, formatted JSON view, status code with color coding (green for 2xx, red for 4xx/5xx), and precise response timing in milliseconds.
One thing I specifically built in: request history. In real debugging sessions, you're iterating on the same endpoint 10, 15, 20 times. Having your last 10 requests accessible in one click saves real time. No more retyping URLs, re-adding headers, reconstructing request bodies.
Step 1
Enter the full API endpoint URL into the URL bar — make sure it starts with https:// or http://. If you're testing a public API, try https://jsonplaceholder.typicode.com/posts/1 to get started immediately.
Step 2
Select the HTTP method from the dropdown on the left — GET for fetching data, POST to create a resource, PUT to update, PATCH for partial updates, and DELETE to remove. If you're unsure, most read operations are GET.
Step 3
Switch to the Headers tab if your API requires authentication or content type — add Authorization: Bearer YOUR_TOKEN or Content-Type: application/json here. Most REST APIs need at least one header.
Step 4
For POST, PUT, or PATCH requests, switch to the Body tab and paste your JSON payload. Make sure it's valid JSON — the tool will highlight syntax errors before you send.
Step 5
Click Send Request. The response panel shows the HTTP status code (200 means success, 401 means unauthorized, 404 means not found, 500 is a server error), response time in milliseconds, all response headers, and the formatted JSON body. Use the Copy button to grab the response for use in your code.
Postman is a great tool. But it's also a 150MB desktop application that requires an account, a workspace, a collection, and three confirmation dialogs before you can send a single request. When I'm deep in a debugging session and I just need to fire a quick GET to see what an endpoint returns, I don't want to context-switch into a full IDE-level tool.
That's the exact problem this tool solves. Open a tab, paste a URL, hit Send. You have your response in under 10 seconds. No install, no login, no project setup. It runs entirely in your browser, which also means your request data never touches our servers — important when you're testing APIs that carry auth tokens or sensitive payloads.
I've found it especially useful in three scenarios: quickly verifying a third-party API's response shape before writing integration code, debugging CORS issues in staging environments, and validating that a newly deployed endpoint is returning the expected status codes. If any of those sound familiar, this tool was made for you.
Zero install — runs entirely in your browser with no account or setup required
CORS bypass via server-side proxy — test any public API without browser security restrictions blocking you
Full request history — re-run any of your last 10 requests in one click without retyping
Supports all HTTP methods — GET POST PUT DELETE and PATCH with complete header and body control
Privacy-first — your request data and API responses are stored only in your browser's local storage and never sent to our servers
Syntax-highlighted responses — JSON output is auto-formatted and color-coded so you spot issues instantly
Response timing — see exact millisecond response times to catch slow endpoints before they hit production
Works offline after initial load — useful when testing local development servers or working on a plane
Debugging backend endpoints during development
Verifying third-party API response structure before writing integration code
Testing authentication flows with Bearer tokens and API keys
Checking HTTP status codes after deploying a new endpoint
Inspecting CORS headers and preflight responses
Validating JSON request body formats for POST and PUT requests
Testing webhook endpoints by simulating incoming payloads
Quick API exploration without writing any code
Example Input
Method: POST
URL: https://jsonplaceholder.typicode.com/posts
Headers:
Content-Type: application/json
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
Body:
{
"title": "Understanding REST API Design",
"body": "REST APIs should be stateless, resource-oriented, and use standard HTTP verbs correctly.",
"userId": 1
}Example Output
Status: 201 Created | Time: 143ms | Size: 218 B
Response Headers:
Content-Type: application/json; charset=utf-8
X-Powered-By: Express
Response Body:
{
"id": 101,
"title": "Understanding REST API Design",
"body": "REST APIs should be stateless, resource-oriented, and use standard HTTP verbs correctly.",
"userId": 1
}⚠Missing Content-Type header on POST requests
Best Practice: If your API returns 415 Unsupported Media Type, add Content-Type: application/json to your request headers.
⚠Testing localhost URLs
Best Practice: This tool uses a server-side proxy, so internal IPs like 127.0.0.1 and localhost are blocked for security. Use a public URL instead.
⚠Forgetting the Bearer prefix in Authorization headers
Best Practice: Use the correct format: Authorization: Bearer YOUR_TOKEN instead of sending only the token string.
⚠Invalid JSON in request body
Best Practice: Ensure all JSON strings use double quotes and remove any trailing commas before sending the request.
⚠HTTP vs HTTPS mismatch
Best Practice: If the API requires HTTPS and you use HTTP, you may get connection errors or redirect loops. Always use the protocol specified by the API.
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Is this REST API Tester free to use?
Yes, completely free — no account, no subscription, no usage limits. I built this because I was tired of hitting Postman's rate limits and paywalls for basic API testing. Open the tool, paste your URL, send the request. That's it.
How does CORS bypass work and is it safe?
When your browser tries to call an API on a different domain, browser security (CORS) often blocks it. Our tool routes your request through a server-side proxy, which makes the call on your behalf and returns the response. Your API key and request data are not logged or stored on our servers — the proxy is stateless and ephemeral.
Can I test APIs that require authentication?
Yes. Add your authentication header in the Headers tab — for JWT-based APIs use Authorization: Bearer YOUR_TOKEN, for API key authentication use whatever header the API specifies (X-API-Key, api-key, etc.). The tool sends your headers exactly as you enter them.
Why can't I test localhost or 127.0.0.1 URLs?
Because our proxy runs on a remote server, it cannot reach your local machine's localhost. To test local APIs, either expose them temporarily using a tunnelling tool like ngrok, or use curl directly in your terminal for local testing. This is a fundamental network constraint, not a limitation we can engineer around.
What is the difference between this tool and Postman?
Postman is a full API development platform — collections, environments, automated testing, team collaboration, CI integration. If you need all of that, Postman is the right tool. This REST API Tester is the opposite: zero setup, open a tab, send a request, done. It's for the quick 30-second test you need while you're in the middle of building something else.
Which HTTP methods does this tool support?
GET, POST, PUT, DELETE, and PATCH — the five standard REST verbs. GET for reading, POST for creating, PUT for full replacement updates, PATCH for partial updates, DELETE for removal. HEAD and OPTIONS are not currently supported but are on the roadmap.
Is my API request data private?
Yes. Your request history is stored only in your browser's localStorage — it never leaves your machine. The proxy used for CORS bypass does not log request bodies, headers, or responses. If you're testing APIs with sensitive tokens or PII, clear your browser history after your session.
The response shows a 401 error — what does that mean?
401 Unauthorized means the API requires authentication and either you didn't provide credentials or the credentials are invalid. Check that you've added the Authorization header with the correct token format. If you just generated the token, double-check it hasn't expired — many JWTs have short TTLs (15 minutes to 1 hour).
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