If you’ve been using Swashbuckle and Swagger UI to document your ASP.NET APIs, you may have noticed that starting with .NET 9, something important is missing—your familiar default tooling. Microsoft introduced first-party OpenAPI support with Microsoft.AspNetCore.OpenApi, replacing Swashbuckle, reducing dependencies, improving performance, and making minimal API documentation much simpler. It’s like giving your APIs a first-class ticket without the baggage fees.
In this 20-minute session, I will provide a high-level overview of what these OpenAPI changes mean for developers and explore viable, customizable alternatives. You will see how the native Microsoft OpenAPI library works and how it compares to Swashbuckle, including interactive tools like Scalar that make documentation and API interaction more modern and developer-friendly.
I will also highlight some key .NET 10 features, such as OpenAPI 3.1 support and multiple output formats, and demonstrate how endpoint and document transformers let you shape, filter, and enrich OpenAPI documentation for different environments, endpoints, or scenarios.
Through live examples, you will learn how to migrate from Swashbuckle, leverage modern tools, and take full advantage of .NET 10’s OpenAPI ecosystem. By the end, you’ll be ready to leave old habits behind and confidently navigate the new OpenAPI landscape.
