Setting up Swagger (ASP.NET Core) using the Authorization headers (Bearer)

Question

ApiKeyScheme was deprecated, in version 5 you can use like this:

services.AddSwaggerGen(c =>
  {
    c.SwaggerDoc("v1", new Info { Title = "You api title", Version = "v1" });
    c.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme
      {
        Description = @"JWT Authorization header using the Bearer scheme. \r\n\r\n 
                      Enter 'Bearer' [space] and then your token in the text input below.
                      \r\n\r\nExample: 'Bearer 12345abcdef'",
         Name = "Authorization",
         In = ParameterLocation.Header,
         Type = SecuritySchemeType.ApiKey,
         Scheme = "Bearer"
       });

    c.AddSecurityRequirement(new OpenApiSecurityRequirement()
      {
        {
          new OpenApiSecurityScheme
          {
            Reference = new OpenApiReference
              {
                Type = ReferenceType.SecurityScheme,
                Id = "Bearer"
              },
              Scheme = "oauth2",
              Name = "Bearer",
              In = ParameterLocation.Header,

            },
            new List<string>()
          }
        });
    var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
    var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
    c.IncludeXmlComments(xmlPath);
});

First of all, you can use Swashbuckle.AspNetCore nuget package for auto generating your swagger definition. (tested on 2.3.0)

After you've installed package, setup it in Startup.cs in method ConfigureServices

services.AddSwaggerGen(c => {
    c.SwaggerDoc("v1", new Info { Title = "You api title", Version = "v1" });
    c.AddSecurityDefinition("Bearer",
        new ApiKeyScheme { In = "header",
          Description = "Please enter into field the word 'Bearer' following by space and JWT", 
          Name = "Authorization", Type = "apiKey" });
    c.AddSecurityRequirement(new Dictionary<string, IEnumerable<string>> {
        { "Bearer", Enumerable.Empty<string>() },
    });

});

Then you can use Authorize button at the top right of the page.

At least you can try to use this package to generate valid swagger definition

TIP!

To avoid always write the keyword Bearer on the Swagger(a.k.a Swashbuckle) auth dialog, like: "bearer xT1...", you can use the code/config below on ConfigureServices(...) method at your Startup class:

using Microsoft.OpenApi.Models;
...


services.AddSwaggerGen(setup =>
{
    // Include 'SecurityScheme' to use JWT Authentication
    var jwtSecurityScheme = new OpenApiSecurityScheme
    {
        Scheme = "bearer",
        BearerFormat = "JWT",
        Name = "JWT Authentication",
        In = ParameterLocation.Header,
        Type = SecuritySchemeType.Http,
        Description = "Put **_ONLY_** your JWT Bearer token on textbox below!",

        Reference = new OpenApiReference
        {
            Id = JwtBearerDefaults.AuthenticationScheme,
            Type = ReferenceType.SecurityScheme
        }
    };

    setup.AddSecurityDefinition(jwtSecurityScheme.Reference.Id, jwtSecurityScheme);

    setup.AddSecurityRequirement(new OpenApiSecurityRequirement
    {
        { jwtSecurityScheme, Array.Empty<string>() }
    });

});

We can make this, only by changing the Type property of the OpenApiSecurityScheme class to:

Type = SecuritySchemeType.**Http**

instead

Type = SecuritySchemeType.**ApiKey**.

Packages:

Swashbuckle.AspNetCore(5.6.3)
Swashbuckle.AspNetCore.SwaggerUI(5.6.3)

I'am using .NET Core 3.1, and hope this helps!

Using ASP.Net Core 3.1, here's what worked for me:

services.AddSwaggerGen(s =>
        {
            s.SwaggerDoc("v1", new OpenApiInfo
            {
                Version = "v1",
                Title = "Chat API",
                Description = "Chat API Swagger Surface",
                Contact = new OpenApiContact
                {
                    Name = "João Victor Ignacio",
                    Email = "[email protected]",
                    Url = new Uri("https://www.linkedin.com/in/ignaciojv/")
                },
                License = new OpenApiLicense
                {
                    Name = "MIT",
                    Url = new Uri("https://github.com/ignaciojvig/ChatAPI/blob/master/LICENSE")
                }

            });

            s.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme
            {
                Description = "JWT Authorization header using the Bearer scheme (Example: 'Bearer 12345abcdef')",
                Name = "Authorization",
                In = ParameterLocation.Header,
                Type = SecuritySchemeType.ApiKey,
                Scheme = "Bearer"
            });

            s.AddSecurityRequirement(new OpenApiSecurityRequirement
            {
                {
                    new OpenApiSecurityScheme
                    {
                        Reference = new OpenApiReference
                        {
                            Type = ReferenceType.SecurityScheme,
                            Id = "Bearer"
                        }
                    },
                    Array.Empty<string>()
                }
            });

        });

There is no need to generate token separate and key in swagger. Swagger support generation part too. Below work for me with asp.net core 3.1 and keycloack auth.

swagger.AddSecurityDefinition(JwtBearerDefaults.AuthenticationScheme, new OpenApiSecurityScheme
{
    Type = SecuritySchemeType.OAuth2,
    Flows = new OpenApiOAuthFlows
    {
        Implicit = new OpenApiOAuthFlow
        {
            AuthorizationUrl = new Uri("https://youauthsrv.com/auth/realms/your-realm/protocol/openid-connect/auth"),
        }
    },
    In = ParameterLocation.Header,
    Scheme = JwtBearerDefaults.AuthenticationScheme,
});

swagger.AddSecurityRequirement(new OpenApiSecurityRequirement
{
    {
        new OpenApiSecurityScheme
        {
            Reference = new OpenApiReference
            {
                Type = ReferenceType.SecurityScheme,
                Id = JwtBearerDefaults.AuthenticationScheme
            }
        },
        new string[] {}
    }
});

in Configure

app.UseSwaggerUI(c =>
{
    c.OAuthClientId("clientname");
    c.OAuthRealm("your-realm");
});