Mock Server GitHub Repositories (2026) · Open Source Tools

Java client for Kubernetes & OpenShift

Terminal API client for HTTP, GraphQL, gRPC, WebSocket and SSE. Plain .http files you can diff and version, with scripted tests, workflows, mocks, recorder, and a CLI runner for CI.

Simulate API failures, throttling, and chaos — all from your command line.

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.

The open source, cloud native tool for API Mocking and Testing. Microcks is a Cloud Native Computing Foundation incubating project 🚀

Test Automation Made Simple

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

A tool for mocking HTTP services

WireMock.Net is a flexible product for stubbing and mocking web HTTP responses using advanced request matching and response templating. Based on WireMock Java, but extended and different functionality. Full documentation can be found at https://wiremock.org/dotnet/.

Official master for the Greenmail project

HTTP mocking library for Rust

A local emulator for enterprise SaaS APIs — Slack, Gmail, Google Drive, GitHub, Jira, Notion, S3 and more — with the real response shapes, pagination, auth and per-document ACLs, over a corpus you supply.

Request mocking tool designed to simplify the process of http request mocking, network debugging, and UI tests for your applications.

A sandbox for the third-party APIs you depend on. Built from the provider's spec, it fails on purpose, and it replays the exact failure production hit.

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.