Mockoon — Desktop API Mocking Made Simple

Introduction

Mockoon is a free, open-source tool for creating mock HTTP APIs without writing code. It was built to solve the problem of frontend developers waiting on backend teams by providing a fast way to simulate any API locally. It runs as a desktop app or a CLI for CI integration.

What Mockoon Does

• Creates mock REST API endpoints with custom HTTP methods, paths, and status codes
• Returns dynamic responses using a built-in templating system with Handlebars
• Simulates latency, errors, and sequential responses for realistic testing
• Supports request logging to inspect incoming calls during development
• Exports and imports environment files for sharing mocks across a team

Architecture Overview

Mockoon is an Electron-based desktop application with an Express.js server running under the hood. Each mock environment spawns an independent Express server on a user-defined port. The CLI version (@mockoon/cli) uses the same Express-based core without the Electron shell, making it suitable for Docker and CI pipelines. Configuration is stored as JSON files.

Self-Hosting & Configuration

• Install the desktop app from the official site or via package managers
• Use the CLI (@mockoon/cli) for headless operation in Docker or CI
• Define environments as JSON files that can be version-controlled
• Configure proxy mode to forward unmatched requests to a real backend
• Set up HTTPS with custom certificates for testing TLS-dependent clients

Key Features

• No-code visual editor for defining routes, headers, and response bodies
• Handlebars-powered response templating with access to request data
• Proxy mode that forwards unmatched routes to a live API server
• CORS pre-configured by default to work with browser-based frontends
• CLI and Docker support for running mocks in automated test pipelines

Comparison with Similar Tools

• Postman Mock Server — cloud-based mocking tied to a Postman account and paid plans
• WireMock — Java-based mock server with more advanced matching but heavier setup
• JSON Server — quick REST API from a JSON file but limited templating and no GUI
• MSW (Mock Service Worker) — intercepts requests in the browser but not a standalone server
• Prism — generates mocks from OpenAPI specs but less flexible for custom responses

FAQ

Q: Is Mockoon free for commercial use? A: Yes. Mockoon is MIT-licensed and free for any use including commercial projects.

Q: Can I run Mockoon in Docker? A: Yes. Use the CLI package (@mockoon/cli) with the official Docker image or build your own.

Q: Does Mockoon support OpenAPI import? A: Yes. You can import OpenAPI/Swagger specifications to auto-generate mock endpoints.

Q: Can multiple developers share the same mock configuration? A: Yes. Export the environment as a JSON file and commit it to version control for the team to share.

Sources

• https://github.com/mockoon/mockoon
• https://mockoon.com/docs/latest/about/