While performing model validation, at times you need to validate values entered in client side controls against server side data. Such a validation is called remote validation. As you might have guessed remote validation uses Ajax to validate the data. Thus validation is initiated on the client side but performed on the server side. The outcome of the validation process is sent back to the client so that the end user can be notified accordingly. In this article we will learn to implement remote validations in ASP.NET Core MVC and ASP.NET Core Razor Pages.