Mockfly vs Mockttp

Mockfly provides hosted mock REST API endpoints for teams building or testing before a backend is ready. An endpoint can return JSON, XML, or files such as PDFs and CSVs, and can select among several responses using rules tied to incoming requests. Mock data can use Faker.js templates or AI-generated JSON. Projects can start from OpenAPI, Swagger, Postman collection, or HAR imports; a Chrome extension can capture browser requests and add selected endpoints. Teams can share and edit mocks, inspect request logs, and review response-body history. For offline work, the mockfly-cli npm package pulls projects to serve locally. A public REST API and MCP server support programmatic mock creation and editing. Mockfly lists API, extension, Linux, self-hosted, and web platforms, and supports REST and WebSocket. The free Starter plan allows 500 requests per day, one project, four endpoints, and two responses per endpoint. Pro costs €15 a month; Team costs €49 a month; Company is listed from €199 a month.

Mockttp is a free, open-source JavaScript library for intercepting, transforming, or testing HTTP requests and responses. It supports integration tests in Node.js and browsers, including transparent proxying and HTTPS. Its tools can stub responses, verify requests, generate self-signed certificates for HTTPS mocking, and mock traffic inside or outside the process. It can also serve as the basis for custom proxies that capture, inspect, or rewrite traffic. For parallel tests, Mockttp can automatically configure ports, mock URLs, and proxy settings. It works with promise-capable testing tools and HTTP clients; Mocha, Chai, and Superagent appear in an example but are optional. Browser tests require an admin server running outside the browser. The setup guide warns against trusting a test certificate authority system-wide or sharing its private key, because either could allow an attacker to impersonate secure connections. Mockttp supports Linux, macOS, Windows, web, and self-hosted use.