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OpenAPI Server

Free#16 of 26 in API Mocking Tools

OpenAPI Server: A focused, open-source choice for Express-based OpenAPI mock services. Ranked #16 of 26 in API Mocking Tools by our editors (7.5/10); pricing: Open source; best for express-based OpenAPI mock services.

7.5/10Editor score

Visit OpenAPI Server

OpenAPI Server7.5 Visit OpenAPI Server

At a glance

Editor score
7.5 / 10
Pricing
Open source
Best for
Express-based OpenAPI mock services
Paid from
Free
Dynamic responses
Yes
Facts checked
20 Sep 2026

Where it wins
- Validates OpenAPI 3 and Swagger 2 specifications
- Supports JSON and JavaScript response mocks
- Proxies unmatched requests to a backend server
Where it doesn't
- Request matching is limited to paths
- Deployment is self-hosted rather than hosted
- Express is the documented integration option

Our verdict on OpenAPI Server

OpenAPI Server is a Node.js development server for mocking APIs from OpenAPI 3 or Swagger 2 specifications. It is suited to frontend prototyping, end-to-end testing, and development work where a backend is unavailable or only partly implemented. The server can run locally through npm, or it can be embedded as an Express application or router. Its core output includes JSON and JavaScript responses, with optional specification and response validation.

Its feature set covers practical local API workflows without moving beyond its focused scope. OpenAPI Server supports HTTP and HTTPS, configurable CLI options, environment variables, .env files, static file serving, and watch mode for restarting when files change. Proxying lets unmatched requests reach a real backend, which supports mixed mock-and-live development environments. Express middleware extensibility is the clearest ecosystem fit, making the product more relevant to Node.js teams already working within Express.

The main trade-off is breadth. Matching is path-based, so teams needing more advanced request-matching behavior may need a different tool. The product is also self-hosted and centered on local development rather than a hosted collaboration workflow. Choose OpenAPI Server when an open-source Node.js server with OpenAPI validation, dynamic JSON or JavaScript mocks, proxying, and Express extensibility fits the workflow. Consider an alternative when hosted management, broader integrations, or more extensive matching capabilities are central requirements.

Your product? Our editors can test OpenAPI Server in depth and publish a review, labelled as paid · from $149/mo →

OpenAPI Server pricing

Plans Open sourceFree Free to use — no paid tier required for the core job.

See plans on github.com

OpenAPI Server fact sheet

Free plan	Not verified
Paid from	Free
Dynamic responses	Yes
OpenAPI import	Yes
Request matching	Path
Mock data generation	Not verified
Local deployment	Yes
Supported protocols	http, https
Deployment	Self-hosted
Built for	Solo, Small business (editorial estimate)
Integrations	1 integrations: Express
Pricing	Open source
Website	github.com
Facts checked	20 Sep 2026

OpenAPI Server integrations

OpenAPI Server lists 1 integrations on its own site.

Express

Alternatives to OpenAPI Server

See all OpenAPI Server alternatives →

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Featured on iTechGuides

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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

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Last updated 7 Oct 2026 · How we research and update