Online API Tester

About CORS: this sends a real browser request, so it's bound by the same-origin rules every web page follows. If the API you're testing doesn't send CORS headers allowing this site, the browser will block the response (usually as a generic network error) — that's a restriction on the API's side, not something this tool can work around. Requests with a JSON body, custom headers (like Authorization), or methods other than GET/POST first send a CORS "preflight"; if that's rejected, the request never reaches the server at all, so nothing runs on the API's side either.