API Tester
API Tester is a free, browser-based tool that lets you send HTTP requests to any REST API endpoint without installing any software. Whether you're debugging a backend service, checking a third-party API, or prototyping a webhook integration, this tool gives you full control over the request — URL, method, headers, query parameters, request body, and authentication — all from a clean web interface. The response comes back with the full HTTP status code, response headers, and body content displayed in a formatted, easy-to-read view. It supports all common HTTP methods including GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS. You can send data as JSON, XML, form data, or raw text, and even toggle between light and dark themes for late-night debugging sessions. No account required, no data stored on our servers — everything runs client-side in your browser for privacy and speed.
What Is
API Tester is a web-based HTTP client that mimics the core functionality of tools like Postman or Insomnia but runs entirely in your browser. You don't need to download anything or create an account. In modern web development, testing APIs is a daily routine. You might need to verify that your authentication endpoint returns the correct JSON, check if a partner's API is responding, or iterate quickly during development without setting up a local testing environment. This tool supports all HTTP methods: - GET: retrieve data from an endpoint - POST: submit data to create resources - PUT: replace existing resources - PATCH: partially update resources - DELETE: remove resources - HEAD: fetch headers only - OPTIONS: discover allowed methods You can customize headers (Content-Type, Authorization, custom headers), add query parameters, set request timeouts, and switch between request body formats (JSON, XML, form-urlencoded, plain text, raw binary). The response panel shows you the HTTP status code with color coding (green for 2xx, yellow for 3xx, red for 4xx/5xx), response time in milliseconds, response size, and full headers. Example JSON POST body: { "username": "[email protected]", "action": "create", "payload": { "items": [1, 2, 3] } } All processing happens locally in your browser — your API keys and request data never leave your machine, ensuring security and privacy.
How to Use
- Enter the full API URL in the address bar (e.g., https://api.example.com/v1/users). Make sure to include the protocol (https://) and any path segments or query parameters you need.
- Select the HTTP method from the dropdown menu on the left side of the URL bar. Choose from GET, POST, PUT, PATCH, DELETE, HEAD, or OPTIONS depending on the action you need to perform.
- Navigate to the Headers tab and add any required HTTP headers. Common examples include 'Content-Type: application/json', 'Authorization: Bearer YOUR_TOKEN', or custom headers like 'X-API-Key: your-key-here'.
- If your request requires a body (POST, PUT, PATCH), click on the Body tab and switch the format type. Enter your request payload — paste JSON for APIs expecting JSON, form data for traditional endpoints, or raw text for any other content type.
- Click the 'Send' button to execute the request. Wait for the response to appear in the bottom panel — you'll see the HTTP status code, response time, response size, formatted response body, and all response headers.
- Inspect the response, modify any parameters if needed, and click the 'Copy' or 'Download' buttons to save the response data for later reference or sharing with your team.
Examples
Input: GET https://api.github.com/users/octocat
Process: Send HTTP GET → Parse JSON response → Display status, headers, body
Result: 200 OK | Login: octocat | Name: The Octocat | Public repos: 8
Input: POST https://httpbin.org/post with JSON body {name:test}
Process: Set Content-Type: application/json → POST body → Parse response
Result: 200 OK | Echoes back {name: test} with request metadata
Input: PUT https://httpbin.org/put with Authorization header
Process: Attach Bearer token → PUT request → Validate response
Result: 200 OK | Confirms resource update with ETag
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Frequently Asked Questions
What HTTP methods are supported by this API tester?
The tool supports all standard HTTP methods including GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS. You can select any of these from the method dropdown next to the URL input. This covers virtually every API interaction pattern you'll encounter in REST APIs, GraphQL endpoints (via POST), and webhook testing scenarios.
Can I send authenticated requests with Bearer tokens or API keys?
Yes, absolutely. You can add any custom header including 'Authorization: Bearer YOUR_TOKEN' or 'X-API-Key: YOUR_KEY'. The headers panel accepts any key-value pair, so it works with Basic Auth headers, custom authentication schemes, and even cookies. Just make sure your tokens are handled carefully — since this runs client-side, they stay on your machine and are never transmitted to our servers.
Does it work with APIs that return XML, CSV, or binary data?
The tool automatically detects and formats JSON responses nicely with syntax highlighting and collapsible sections. For XML responses, it displays them with basic formatting. Binary responses like images or PDFs will show as raw data or can be downloaded directly. If you need to test file uploads, you can switch the body type to form-data and attach files from your local system.
What data formats can I send in the request body?
You can send JSON (with syntax highlighting), XML, URL-encoded form data, plain text, or raw binary data. Switch between formats using the body type selector. For POST requests to modern REST APIs, JSON is the most common format. For older APIs or form submissions, use URL-encoded form data. For file uploads, use the multipart/form-data option.
Is my data and API key secure when using this tool?
Yes, completely. The entire tool runs client-side in your browser using JavaScript. No request data, headers, API keys, or responses are ever sent to our servers. Your credentials and testing data stay entirely on your local machine. We don't store any logs, cookies, or session data. It's as secure as testing APIs from your own terminal, but with a visual interface.