Mockfly vs MockServer

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.

MockServer is a free, self-hosted tool for mocking and proxying HTTP, HTTPS, and gRPC services during isolated testing. It can verify requests as well as stand in for services. Teams can generate mocks and validate traffic against OpenAPI or Swagger contracts, or import recorded sessions from browser HAR files and Postman collections. Beyond HTTP services, it can mock gRPC, AsyncAPI brokers such as Kafka, MQTT, and AMQP, and OAuth2/OIDC providers. Its protocol coverage includes HTTP/1.1, HTTP/2, HTTPS, SOCKS, and experimental HTTP/3, which uses a separate UDP port. For fault-oriented testing, it can add latency, errors, dropped connections, and malformed responses to mocked or proxied traffic. Deployment options include Docker, an executable JAR, Helm/Kubernetes, Testcontainers, Homebrew, and a JVM-less bundle. A web dashboard displays logs, expectations, and recorded traffic; Prometheus metrics and OpenTelemetry tracing are available for shared environments. Each instance includes an MCP server at /mockserver/mcp. The /mockserver/status and /mockserver/ready probes remain reachable without authentication or authorization.