mitmproxy : mitmproxy is your swiss-army knife for debugging, testing, privacy measurements, and penetration testing. It can be used to intercept, inspect, modify...
hurl.it : Hurl.it makes HTTP requests.
Choose the request method, customize headers and POST parameters, add basic authorization or OAuth credentials, and even ...
httpbin.org : A simple HTTP Request & Response Service.
Pact : Fast, easy and reliable testing for integrating web apps, APIs and microservices. Pact is a code-first tool for testing HTTP and message integrations ...
httpbin : Testing an HTTP Library can become difficult sometimes. PostBin.org is fantastic for testing POST requests, but not much else. This exists to cover al...
toxy is a fully programmatic and hackable HTTP proxy to simulate server failure scenarios and unexpected network conditions, built for node.js/io.js.