I am currently developing a .net core web API that will use a swagger as its documentation. Everything was perfect, except almost of the request method has a required data that was in the header. My problem was how to add an input header in the Swagger UI. After a few research, I found it. Here's how to do it. Create a filter class that implement IOperationFilter public class MyCustomHeaderFilter : IOperationFilter { public void Apply(OpenApiOperation operation, OperationFilterContext context) { if (operation.Parameters != null) { operation.Parameters.Add(new OpenApiParameter { Name = "FilterName", In = ParameterLocation.Header, Description = "access token", Required = false, }); } } } Register the class in swagger using OperationFilter ...