Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
WireMock - WireMock - a web service test double for all occasions.
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.
Mockoon - Mock servers in seconds
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.
Mocko.dev - Proxy your API, choose which endpoints to mock in the cloud and inspect traffic, for free. Speed up your development and integrations tests.