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.NET 9–OpenAPI and Scalar–Introduction

With the release of .NET 9, Microsoft has removed Swashbuckle from the default Web API templates. If you have never heard about Swashbuckle before, it allowed you to generate OpenAPI metadata for your web api's. Although I had no complaints using the Swagger UI, I decided to use the opportunity to have a look at library, Scalar, to generate an UI based on the OpenAPI documentation.

In this post, I’ll walk you through my transition from Swashbuckle to Scalar, highlighting the benefits, challenges, and key implementation steps.

Why the change?

Microsoft decided to drop Swashbuckle due to maintenance issues and a shift toward integrated OpenAPI support. While Swashbuckle provided automatic documentation, Swagger UI integration, and customizability, Scalar introduces a sleek UI, mobile-friendly interface, and enhanced search capabilities. Scalar not only provides great integration for .NET but also works on a lot of other platforms.

Setting Up Scalar in .NET 9

To integrate Scalar into your .NET 9 Web API, follow these steps:

  • Start by installing the required packages

dotnet add package Scalar.AspNetCore

dotnet add package Microsoft.AspNetCore.OpenApi

  • Next step is to configure the OpenAPI integration in our Program.cs file.
  • The configuration above will generate a default v1.json OpenAPI metadata file that is accessible at /openapi/v1.json.

  • The last step is to access the API documentation through Scalar. You can access the Scalar UI by browsing to /scalar/v1, which provides an interactive API documentation experience.
    • Remark: the v1 part should match with the name of the OpenApi document that is used in the OpenApi configuration.

In a next post I look at how we can further tweak the experience when using the built-in OpenAPI support and Scalar. Stay tuned!

More information

Scalar - Document, Test & Discover APIs

Announcement: Swashbuckle.AspNetCore is being removed in .NET 9 · Issue #54599 · dotnet/aspnetcore

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