API Request Tester

What this tool does

API Request Tester sends an HTTP request (any method, custom headers, request body) directly from your browser using fetch(), showing the response status, headers and pretty-printed body, a lightweight, install-free way to quickly test a CORS-enabled API endpoint.

Testing a REST API endpoint quickly, especially a public one or one you’re actively developing, doesn’t always need a full dedicated API client installed, a browser can make the exact same fetch() request your own frontend code would.

This tool sends a configurable HTTP request (method, custom headers, body) directly from your browser and displays the response status, headers and a pretty-printed body, right in the page, no install, account or extension required.

How to use API Request Tester

1. Choose the Method and enter the URL.
2. Add any Headers (one per line, Key: Value format).
3. For non-GET requests, enter a Body.
4. Press Send and review the response.

Tips for better results

• CORS (Cross-Origin Resource Sharing) is the single biggest limitation here, a target server must explicitly allow browser-based cross-origin requests for this to succeed; a request that fails here may still work fine from a backend or a dedicated API client.
• A JSON response body is automatically pretty-printed for readability; a non-JSON response is shown exactly as received.
• Response headers can appear incomplete on a cross-origin request, browsers only expose a limited, safe subset of headers to JavaScript unless the server explicitly opts in via Access-Control-Expose-Headers.
• Nothing you send passes through any Toolew server, the request goes directly from your browser to the target API, exactly as if your own frontend code had made it.

Common use cases

• Quickly testing a public API endpoint’s response without installing a dedicated tool.
• Checking whether an API you’re developing correctly handles CORS for browser-based requests.
• Inspecting the exact response headers and body an endpoint returns for debugging.
• Testing different HTTP methods or request bodies against an endpoint during development.

Common mistakes to avoid

• Testing a protected or internal API that doesn’t send CORS headers and assuming the tool is broken when it fails, that’s the browser’s CORS policy correctly blocking the cross-origin request, not a bug; such APIs need to be tested from a backend or dedicated API client instead.
• Forgetting to set a Content-Type header (like application/json) when sending a JSON body, some APIs require it explicitly to parse the body correctly.
• Assuming all response headers are visible; cross-origin responses only expose a browser-defined safe subset by default unless the server explicitly exposes more via CORS configuration.