API Tester
Send HTTP requests with a custom method, headers and body, and inspect the status, headers, timing and body of the response — a lightweight, free API tester that runs entirely in your browser.
What is this tool for?
This API tester lets you send real HTTP requests — GET, POST, PUT, PATCH, DELETE — with custom headers and a request body, then inspect the exact status code, response headers, timing and body. It's useful for quickly checking an endpoint, debugging a webhook, or verifying request/response shapes without installing a desktop app.
A note on CORS
Because this runs entirely in your browser, requests are subject to the same CORS (Cross-Origin Resource Sharing) rules as any web page. If a request fails with a generic network error, the target server most likely doesn't send an Access-Control-Allow-Origin header for browser origins — this is a security restriction enforced by the browser, not a bug in this tool. It works reliably for your own APIs (in local dev or with CORS enabled), same-origin endpoints, and CORS-friendly public APIs.
Frequently Asked Questions
Why do I get "Failed to fetch"?
This almost always means the target server blocked the cross-origin request (no CORS headers), or the URL is unreachable/uses a self-signed certificate. Check the CORS Tester tool to see exactly what headers a server returns.
Is my request data sent through Encoder.guru's servers?
No. The request goes directly from your browser to the target URL using the standard fetch() API. Encoder.guru has no backend involved in the request.
Can I send authentication headers?
Yes — add an Authorization header row with a Bearer token, API key, or Basic auth value like you would in any HTTP client.