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MockServer

mock-server.com

Free plan WebWindowsmacOSLinuxAPISelf-hosted
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Spec score 8.0 #10 of 26 in API Mocking Tools

What it is

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.

Spec sheet

Purpose
MockServer mocks and proxies HTTP, HTTPS and gRPC services for fast, isolated and deterministic testing.Read 1 Oct 2026 · mock-server.com
Deployment
It can run through Docker, an executable JAR, Helm/Kubernetes, Testcontainers, Homebrew or a JVM-less binary bundle.Read 1 Oct 2026 · mock-server.com
AI integration
Every instance includes an MCP server at /mockserver/mcp for assistants such as Claude Code, Cursor, Windsurf, Cline and OpenCode.Read 1 Oct 2026 · mock-server.com
API contracts
Mocks can be generated and traffic validated from OpenAPI or Swagger specifications.Read 1 Oct 2026 · mock-server.com
Chaos testing
It injects latency, error responses, dropped connections and malformed responses into mocked or proxied HTTP, gRPC and TCP traffic.Read 1 Oct 2026 · mock-server.com
Client integrations
Official clients are available for Java, JavaScript, Python, Ruby, Go, .NET, Rust and PHP, alongside the CLI and REST API.Read 1 Oct 2026 · mock-server.com
Control-plane security
Control-plane requests can be authenticated with mutual TLS, JWT or both, and authorization can map OIDC scopes or groups to roles.Read 1 Oct 2026 · mock-server.com
Core roles
It can act as a mock, proxy and request-verification tool.Read 1 Oct 2026 · mock-server.com
Imports
Recorded traffic can be imported from browser HAR files and Postman collections.Read 1 Oct 2026 · mock-server.com
Messaging and identity
It can mock gRPC services, AsyncAPI brokers including Kafka, MQTT and AMQP, and OAuth2/OIDC providers.Read 1 Oct 2026 · mock-server.com
Observability
A built-in web dashboard shows live logs, expectations and recorded traffic, while Prometheus metrics and OpenTelemetry tracing support shared environments.Read 1 Oct 2026 · mock-server.com
Protocol support
It supports HTTP/1.1, HTTP/2, HTTPS, SOCKS and experimental HTTP/3, with HTTP/3 using a separate UDP port.Read 1 Oct 2026 · mock-server.com
Security limitation
The /mockserver/status and /mockserver/ready health probes are always reachable without authentication or authorization.Read 1 Oct 2026 · mock-server.com
Source and support
GitHub hosts the source code, feature requests, issues, pull requests and releases.Read 1 Oct 2026 · mock-server.com
Template safety
Velocity class loading is disabled by default and JavaScript templates cannot resolve Java classes unless explicitly allowed.Read 1 Oct 2026 · mock-server.com

Plans and prices

Free and open-source Free self-hosted · no SaaS account Read 1 Oct 2026 · mock-server.com

Every MockServer plan and price →

Strong points and limits

Strong points

  • Free, open-source self-hosted plan.
  • Generates mocks from OpenAPI or Swagger specifications.
  • Imports HAR files and Postman collections.
  • Supports gRPC, AsyncAPI brokers, and OAuth2/OIDC.
  • Dashboard includes live logs and recorded traffic.

Limits

  • HTTP/3 support is experimental and uses a separate UDP port.
  • Status and readiness probes are unauthenticated.
  • Self-hosted deployment requires operating an instance.

Who it suits

MockServer suits teams that need to simulate dependencies, validate API contracts, or inject failures into test traffic. Its self-hosted deployment options and client libraries cover several languages and environments.

Verdict

MockServer combines service simulation, contract validation, and fault injection in a free self-hosted package. The unauthenticated health probes are an important control-plane caveat to account for.

Where Specifiction places it

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