In this article, we are going to implement Blazor WebAssembly cookie authentication with Facebook(external login provider). Click here for - Part-1 Blazor WebAssembly authentication with .net core cookie. Install Facebook NuGet In API Project: Let's install the Microsoft Facebook Authentication package. .NET CLI Command: dotnet add package Microsoft.AspNetCore.Authentication.Facebook --version 6.0.3 Package Manager: Install-Package Microsoft.AspNetCore.Authentication.Facebook -Version 6.0.3 Register API Wih Facebook: To enable Facebook authentication we have to register our API project with Facebook. So following are facebook registration steps. Step1: Go to the Facebook Developer page at "https://developers.facebook.com/apps/". Step2: Go to the 'My Apps' menu and click on the 'Create App' button. Step3: In the 'Create An App' section, choose the 'Consumer' option and then click on the 'Next' button. Step4: In the 'Detail