Request inspector - Debug web hooks, http clients

GoReplay - GoReplay is an open-source tool for capturing and replaying live HTTP traffic into a test environment.

Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.

Testlio - Testlio is a community of expert testers that help companies release their apps with highest confidence

MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.

Assertible - Assertible software provides you with a simple and quick way to monitor your web services. It comes with automated QA tools that users can utilize to test and monitor their web services on different platforms and environments.