With the removal of Swashbuckle.AspNetCore in .NET 9, developers are left wondering about alternative solutions for API documentation. One of the rising stars in this domain is Scalar, a modern and robust OpenAPI tool that offers a streamlined experience for creating, maintaining, and publishing API documentation. In this article, we will delve into the world of Scalar and explore its features, benefits, and usage in .NET 9. **What is Scalar?** Scalar is an OpenAPI tool that enables developers to generate beautifully formatted API documentation from their Swagger OpenAPI specifications. It offers a simple and intuitive interface for creating, editing, and customizing API documentation, making it an excellent alternative to Swashbuckle.AspNetCore for .NET 9. **Key Features of Scalar** Scalar offers a range of features that make it an attractive choice for developers, including: **Customizable templates**: Scalar allows developers to create custom templates for their API documentation, providing a high degree of flexibility and control. **Documentation themes**: Scalar supports a range of documentation themes, enabling developers to tailor the look and feel of their API documentation to their specific needs. **Live coding**: Scalar integrates seamlessly with live coding, allowing developers to monitor changes to their API documentation in real-time. **Integrations**: Scalar is compatible with a wide range of .NET platforms, including .NET Core, .NET Framework, and .NET 5. **Usage in .NET 9** To use Scalar in .NET 9, developers can install the Scalar NuGet package using Package Manager Console or the .NET CLI. Once installed, they can create a new Scalar file and configure it to interact with their .NET 9 project. Scalar supports a range of project types, including ASP.NET Core Web API, ASP.NET Core MVC, and .NET Core Console. **Conclusion** In conclusion, Scalar presents a compelling alternative to Swashbuckle.AspNetCore in .NET 9. Its intuitive interface, customizable templates, and support for live coding and integrations make it an attractive choice for developers seeking to create robust and maintainable API documentation. By leveraging Scalar's features, developers can create beautifully formatted API documentation that accurately reflects their projects and their teams.