Webhook Tester : Webhook Tester allows you to easily test webhooks and other types of HTTP requests.
Requestdiff : Differentiate HTTP headers and content body of two GET URLs.
patchbay : patchbay.pub is a free web service you can use to implement things like static site hosting, file sharing, cross-platform notifications, webhooks hand...
TraceKit : Not all browsers support stack traces on error objects, but TraceKit squeezes out as much useful information as possible and normalizes it.
toxy : toxy is a fully programmatic and hackable HTTP proxy to simulate server failure scenarios and unexpected network conditions, built for node.js/io.js.
RequestBin gives you a URL that will collect requests made to it and let you inspect them in a human-friendly way.
Use RequestBin to see what your HTTP client is sending or to inspect and debug webhook requests.