What Is Scalar? Why Use Scalar Instead of Swagger UI in ASP.NET Core 10
Scalar is an open-source API Reference UI that replaces Swagger UI, and it is what Microsoft recommends for ASP.NET Core from .NET 9 onward. Starting with .NET 9, Microsoft removed Swashbuckle (Swagger UI) from the default Web API template and replaced it with Microsoft.AspNetCore.OpenApi combined with Scalar. This post explains the reasoning behind that change, compares Scalar against Swagger UI feature by feature, and walks through setting Scalar up in ASP.NET Core 10 — both for a brand new project and as a migration from an existing one.
If you created a new ASP.NET Core Web API project on .NET 9 or .NET 10 and were surprised to find Swagger UI missing, you are not alone. Microsoft deliberately replaced Swashbuckle with a native OpenAPI pipeline, and Scalar is the UI recommended alongside it.
