Mockoon is a free, open-source tool that lets developers design and run mock REST APIs on their own machine instead of waiting on a live backend. It pairs a desktop application for building mocks with a command-line interface, Docker image, and libraries for running those mocks in CI pipelines and on servers. The project started in 2017, has been downloaded more than one million times, and its canonical repository is mockoon/mockoon under the MIT license.[1][2][3][4]
Quick verdict
Mockoon is a free, MIT-licensed tool for running mock REST APIs locally with no account, and its desktop GUI, rule-based matching, templating, and CLI/Docker path into CI suit developers who want offline-first mocks. Team collaboration, managed deployments, and OIDC single sign-on are paid Pro capabilities starting at five licenses, so teams needing hosted workspaces on a free tier should stay with an incumbent like Postman. If local-first mocking fits your workflow, choose Mockoon; if hosted collaboration is the requirement, choose the cloud incumbent.[1][2][3][4]
Key features
Design mocks in a desktop GUI Create unlimited mock APIs with unlimited routes on Windows, macOS, and Linux, and run them in parallel from an intuitive interface with a five-minute getting-started path.[1][2]
Match requests with rules Serve multiple rules-triggered or random responses per route with any headers, body, or HTTP status code, including regex routes in ExpressJS syntax.[1][2]
Generate dynamic data with templating Build stateful, realistic responses with the templating system instead of hand-writing every payload.[1][2]
Record, replay, and proxy Forward requests to real APIs, record and replay them, and partially mock endpoints through proxy mode.[1][2]
Keep mocks in the pipeline Run the same mocks headlessly with the CLI, the Docker image, the GitHub Action, or serverless runtimes for CI and integration testing.[1][2]
Speak OpenAPI Import and export Swagger/OpenAPI definitions so mocks stay aligned with the API design workflow.[1][2]
Simulate state and behavior Perform RESTful CRUD operations on fake JSON databases and model asynchronous flows with callbacks and webhooks.[1][2]
Control the transport details Serve over TLS with a custom certificate, send CORS headers automatically, and add latency at environment or route level to test resilience and edge cases.[1][2]
Who will love it
Frontend developers building against APIs that are unfinished, rate-limited, or expensive to call in development.[1][2][3]
Developers who need a controlled environment with predictable responses, status codes, and latencies for integration testing and edge-case simulation.[1][2][3]
Teams that want the same mocks running in CI pipelines, Docker containers, or GitHub Actions without a cloud dependency.[1][2][3]
Who should avoid it
Teams that need hosted collaboration, shared workspaces, or cloud sync without paying: those are Pro features starting at five licenses.[1][2]
Organizations that require single sign-on or audit trails on the free tier: OIDC SSO and audit events are Pro-only.[1][2]
Anyone needing mock protocols beyond HTTP REST-style APIs, which is not Mockoon's documented scope.[1][2]
Questions worth asking
Is Mockoon really free and open source?
Does Mockoon need an internet connection or an account?
How do mocks get into CI or a server?
What does Mockoon Pro cost?
The Team plan is EUR 10 per license per month excluding tax, billed annually with a minimum of five licenses and a 14-day trial. Enterprise pricing is custom and can include managed cloud deployment.[1]
Sources and editorial review
Source research. Reviewed on October 11, 2026. Written by Sanjib Sah. AI assisted; reviewed by a human editor.
We have not run or tested this product.
- Mockoon homepage - create mock APIs in seconds
official · Observed October 11, 2026
Official homepage: scope, aggregate ratings, download entry points.
- What is Mockoon?
official · Observed October 11, 2026
Official explainer: what Mockoon is, desktop plus CLI and Docker delivery.
- Mockoon complete list of features
official · Observed October 11, 2026
Official features catalogue: rules, templating, proxy, OpenAPI, TLS, latency.
- Mockoon Pro pricing
official · Observed October 11, 2026
Official pricing: free core scope, Pro team plan terms, enterprise custom pricing.
- Mockoon FAQ
official · Observed October 11, 2026
Official FAQ: licence, offline use, CI delivery, Pro cost.
- Comparison between Mockoon and Postman's API mocking services
official · Observed October 11, 2026
Official vendor comparison: Mockoon versus Postman cloud mock endpoints.
- Download Mockoon desktop
official · Observed October 11, 2026
Official download page: desktop, CLI, Docker, and server distributions.
- GitHub API: mockoon/mockoon repository record
official · Observed October 11, 2026
Public repository record mockoon/mockoon: licence, releases, activity.