Swagger UI is free and open source tool to generate interactive API documentation for API integration and testing


Swagger UI is a powerful and widely-used open-source tool for API documentation and testing. It is part of the Swagger ecosystem, which includes Swagger Editor, Swagger Codegen, and SwaggerHub. Swagger UI provides a user-friendly interface for exploring and interacting with APIs, allowing developers to visualize and test their API endpoints directly from the browser. With its interactive documentation, Swagger UI enhances the developer experience by providing real-time feedback on API requests and responses. This makes it an invaluable tool for both development and quality assurance processes.


Swagger UI comes with a host of features that make it a versatile tool for API automation and documentation:

  1. Interactive API Documentation: Swagger UI generates interactive API documentation from OpenAPI (formerly Swagger) specifications. This documentation allows users to try out API endpoints directly from the browser.
  2. Real-Time API Testing: Users can send API requests and receive responses in real-time, providing immediate feedback on the functionality and performance of API endpoints.
  3. Support for Various HTTP Methods: Swagger UI supports a wide range of HTTP methods, including GET, POST, PUT, DELETE, PATCH, and more, ensuring comprehensive testing capabilities.
  4. Parameter and Schema Validation: The tool validates request parameters and schemas against the API specification, helping to ensure that requests are correctly formed and adhere to the defined standards.
  5. Customizable Interface: Developers can customize the Swagger UI interface to match their branding and preferences, enhancing the user experience.
  6. OAuth2 Authentication: Swagger UI supports OAuth2 authentication, allowing secure access to protected API endpoints and facilitating testing of APIs with complex authentication mechanisms.
  7. Automatic Documentation Updates: When the OpenAPI specification is updated, Swagger UI automatically reflects these changes in the documentation, ensuring that the documentation is always up-to-date.
  8. Client SDK Generation: Swagger UI can be integrated with Swagger Codegen to generate client SDKs in various programming languages, streamlining the development process.
  9. Error Handling and Debugging: Detailed error messages and debugging information are provided for failed requests, aiding in the identification and resolution of issues.
  10. Extensibility: Swagger UI supports plugins and extensions, allowing developers to extend its functionality to meet specific needs.


Swagger UI offers several advantages that make it a preferred choice for API documentation and testing:

  1. User-Friendly Interface: Its clean and intuitive interface makes it easy for users to explore and test APIs without extensive technical knowledge.
  2. Open Source and Free: As an open-source tool, Swagger UI is free to use, which makes it accessible to a wide range of users, from individual developers to large enterprises.
  3. Seamless Integration: Swagger UI integrates seamlessly with other tools in the Swagger ecosystem, such as Swagger Editor and SwaggerHub, providing a comprehensive solution for API development and management.
  4. Interactive Documentation: The ability to interact with API endpoints directly from the documentation enhances the developer experience and speeds up the testing process.
  5. Broad Adoption and Community Support: Swagger UI is widely adopted and has a large community of users and contributors, ensuring continuous improvement and ample resources for learning and troubleshooting.
  6. Standards Compliance: Swagger UI adheres to the OpenAPI specification, which is a widely accepted standard for API documentation, ensuring consistency and interoperability.
  7. Enhanced Collaboration: The interactive documentation facilitates better collaboration between developers, QA teams, and other stakeholders by providing a clear and accessible view of the API.


Despite its strengths, Swagger UI has some limitations:

  1. Performance Issues with Large Specifications: Swagger UI can become sluggish and less responsive when handling very large API specifications, which can hinder productivity.
  2. Limited Advanced Testing Features: While it excels at documentation and basic testing, Swagger UI lacks some advanced testing features such as automated test scripts and load testing, which are available in other API testing tools.
  3. Dependency on OpenAPI Specification: Swagger UI relies on the OpenAPI specification for generating documentation. APIs not documented using OpenAPI cannot be visualized or tested with Swagger UI.
  4. Customization Complexity: While customization is possible, it can be complex and time-consuming, especially for developers who are not familiar with the tool’s internals.
  5. Lack of Built-In CI/CD Integration: Unlike some other API testing tools, Swagger UI does not have built-in integration with CI/CD pipelines, requiring additional setup for automated testing in development workflows.

Using Swagger UI to document and test an API is straightforward. Here’s an example of how to use Swagger UI to explore and test a REST API:

Setting Up Swagger UI:

  1. Install Swagger UI: You can host Swagger UI locally by downloading the repository from GitHub or using a CDN. Alternatively, you can use the online version.
  2. Create OpenAPI Specification: Define your API endpoints, parameters, and schemas in an OpenAPI specification file (e.g., swagger.yaml or swagger.json).

Example OpenAPI Specification:

openapi: 3.0.0
  title: Sample API
  description: API documentation for the Sample API
  version: 1.0.0
      summary: Retrieve a list of users
          description: A list of users
                type: array
                  type: object
                      type: integer
                      type: string
                      type: string

Launching Swagger UI:

  1. Local Setup: Place your OpenAPI specification file in the dist folder of the Swagger UI directory and open index.html in a web browser. Ensure the url parameter in index.html points to your specification file.
  2. Online Version: Visit Swagger UI and paste your OpenAPI specification URL or JSON/YAML content.

Interacting with the API:

  1. Explore Endpoints: Navigate through the endpoints listed in the Swagger UI interface.
  2. Send Requests: Click on an endpoint, fill in any required parameters or authentication details, and click “Try it out” to send a request.
  3. View Responses: Review the response data, status code, and headers in the UI.



Swagger UI itself is free and open-source, but it can be part of a broader suite of tools with additional pricing models:

  1. Free and Open Source: Swagger UI is free to use under the Apache 2.0 license, making it accessible to everyone.
  2. SwaggerHub: For those looking for a more integrated solution with additional features like API design, collaboration, and hosting, SwaggerHub offers various pricing plans starting from $75 per month for small teams, with custom pricing for larger organizations.

Swagger UI is recommended for:

  1. API Developers: Its interactive documentation and real-time testing capabilities make it an invaluable tool for API developers who need to visualize, test, and debug their APIs efficiently.
  2. Quality Assurance Teams: QA teams can use Swagger UI to validate API endpoints, test various scenarios, and ensure that APIs function as expected.
  3. Technical Writers: Technical writers responsible for creating API documentation will find Swagger UI’s auto-generated documentation features highly useful.
  4. Small to Medium-Sized Teams: Teams that require a cost-effective, open-source solution for API documentation and testing will benefit from Swagger UI’s capabilities.
  5. Educational Purposes: Students and educators can use Swagger UI to learn about API development and testing, given its ease of use and comprehensive documentation.


Swagger UI stands out as a premier tool for API documentation and testing. Its user-friendly interface, combined with a robust set of features, makes it an essential asset for developers and QA professionals. While it may not offer all the advanced testing capabilities of more specialized tools, its focus on interactive documentation and real-time testing makes it an excellent choice for many use cases.

Whether you are an individual developer, part of a small team, or involved in large-scale enterprise projects, Swagger UI provides the tools you need to document, explore, and test APIs effectively and efficiently.

About the author
Irfan Ahmad

Irfan Ahmad

Software Quality Leader | Helping software teams to deliver with speed, security and scale.

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