Swashbuckle swagger asp net core failed to load api definition


Swashbuckle is a popular used in ASP.NET Core applications to generate documentation for APIs. However, sometimes you may encounter issues where Swashbuckle fails to load the API definition. In this article, we will explore some common causes of this problem and provide solutions with examples.

Missing or Incorrect

One possible reason for Swashbuckle failing to load the API definition is missing or incorrect configuration. Ensure that you have properly configured Swashbuckle in your ASP.NET Core application. Here is an example of how to configure Swashbuckle in the Startup.cs file:

public void ConfigureServices(IServiceCollection services)
    services.AddSwaggerGen(c =>
        c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });

Make sure that you have provided the correct API version and title in the SwaggerDoc . Additionally, ensure that you have the Swagger middleware in the Configure method:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    // Other middleware configurations

    app.UseSwaggerUI(c =>
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");

    // Other configurations

Here, the SwaggerEndpoint method specifies the URL where the Swagger JSON file is located. Ensure that the URL matches the configured API version and title.

Missing XML Documentation

Another reason for Swashbuckle failing to load the API definition is missing XML documentation. Swashbuckle uses XML comments to generate the API documentation. Ensure that you have enabled XML documentation generation in your project settings. To enable XML documentation, these steps:

  1. Right-click on your project in Visual Studio and select “”.
  2. In the “Build” tab, check the “XML documentation file” option.
  3. Save the project settings.

After enabling XML documentation, rebuild your project to generate the XML file. Swashbuckle will automatically pick up the XML file and use it to generate the API documentation.

API Routes

Invalid API routes can also cause Swashbuckle to fail in loading the API definition. Ensure that your API routes are correctly defined and follow the routing conventions. Here is an example of a correct API route definition:

public  GetProducts()
    // API logic

Make sure that you have specified the correct HTTP verb attribute (e.g., [HttpGet], [HttpPost]) and the route attribute (e.g., [Route(“api/products”)]). Swashbuckle relies on these attributes to generate the API documentation correctly.


In this article, we have explored some common causes of Swashbuckle failing to load the API definition in ASP.NET Core applications. We have provided solutions with examples for missing or incorrect configuration, missing XML documentation, and invalid API routes. By following these guidelines, you be able to resolve any issues related to Swashbuckle and successfully generate Swagger documentation for your APIs.

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