mocko-app/mocko

mocker-api that creates mocks for REST APIs. It will be helpful when you try to test your application without the actual REST API server.

Mockoon is the easiest and quickest way to run mock APIs locally. No remote deployment, no account required, open source.

MockServer is an HTTP(S) mock server and proxy for testing that lets you mock APIs, inspect and modify live traffic, and inject failures. It supports HTTP/1.1, HTTP/2, gRPC, WebSockets, TCP and more on a single port, with additional support for HTTP/3, message brokers, and AI/LLM APIs.

Open-source OpenAPI mock server with cloud hosting and local modes for development, testing, and CI. Generates realistic API responses from specs with latency simulation, error injection, proxy fallback, and request validation. Validated against 2,200+ real-world OpenAPI specs.

Smocker is a simple and efficient HTTP mock server and proxy

Free, 10.5MB, containerized, self-hosted mock server.

A tool for mocking HTTP services

LiveMock is a comprehensive tool for API development and testing, offering mock data, request proxying, and logging, to streamline workflows and track traffic.

Insomnia Mockbin is the underlying backend for the API mocks capability of Insomnia. It is built and used by Kong, the author of the open-source Kong Gateway.