NSwag review
An open-source .NET toolchain for generating API specifications, clients, and controllers.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
NSwag is an open-source toolchain for creating Swagger and OpenAPI specifications and generating code from them. It suits ASP.NET teams that need to produce API documents from Web API or ASP.NET Core controllers, or create C# and TypeScript clients and ASP.NET controllers from an OpenAPI specification. The project supports Swagger 2.0 and OpenAPI 3.0, with CLI and MSBuild workflows for teams that want generation in their development process, plus NSwagStudio for configuring generation through a Windows graphical interface.
Its breadth across the API lifecycle is the main distinction: NSwag can generate specifications from ASP.NET controllers, serve those specifications through ASP.NET and OWIN middleware, and generate clients or controllers from the resulting documents. NuGet, NPM, MSBuild, ASP.NET Core, and OWIN integrations make it a fit for .NET-centered projects that also need TypeScript client generation. Teams choosing it should be comfortable with the C# and TypeScript focus; it is not a general-purpose multi-language code generator.
NSwag is open source and has a free plan, with deployment listed as self-hosted and desktop rather than a paid SaaS service. Automation is available through command-line tools and MSBuild targets, while NSwagStudio offers a visual configuration option on Windows. Support is through community channels and documentation. Pick NSwag when OpenAPI-based generation needs to fit an ASP.NET workflow; teams seeking a broader language range, or a graphical interface on macOS or Linux, should consider alternatives.
NSwag pros and cons
- Where it wins
- Generates Swagger 2.0 and OpenAPI 3.0 specifications from ASP.NET controllers
- Creates C# and TypeScript clients from OpenAPI specifications
- Offers CLI, MSBuild, middleware, and a Windows graphical interface
- Where it doesn't
- NSwagStudio is available only on Windows
- Generation focuses on C# and TypeScript
- Support channels are community resources and documentation
NSwag fact sheet, pricing and score →
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