MockAPI Dog is a free tool that enables developers to create and deploy mock REST APIs and LLM streaming endpoints instantly without requiring any signup or authentication. It serves as a solution for quick API prototyping and testing AI integrations, allowing users to generate endpoints immediately upon visiting the website.

The tool supports all standard HTTP methods including GET, POST, PUT, DELETE, PATCH, HEAD, and OPTIONS. It features REST API mocking with JSON responses and LLM streaming endpoint mocking compatible with OpenAI, Anthropic, and other providers. Additional capabilities include custom HTTP status codes, a built-in JSON editor with syntax highlighting, artificial delay simulation for testing slow network conditions, random error rate testing, conditional errors based on request headers, and CORS enabled for cross-origin requests.

The platform operates by automatically generating a unique short code for each endpoint, allowing users to configure their response by selecting either REST API with JSON or LLM streaming with AI-like responses. After clicking save, the mock API becomes live immediately and can be used anywhere by copying the URL. This approach eliminates the need for registration, API keys, or configuration files.

Benefits include enabling frontend development without waiting for backend APIs, testing AI/LLM integrations without burning through API credits, simulating different responses and error scenarios, rapid prototyping for idea validation, and providing stable endpoints for learning and CI/CD testing. Use cases cover testing AI chatbot integration, error handling scenarios, building frontends without completed backends, and workshop/training exercises.

The product targets frontend developers, testers, AI builders, and anyone needing to practice API integration without complex setup. It's designed for development, testing, and prototyping purposes rather than production use, with endpoints remaining active as long as they're being used.