.Net Core application JSON file configuration technique has come into picture by replacing traditional way like Web.Config file approach. By default application loads "appSettings.json" file on startup. If we have defined environment variable then application also loads environmental specific json files like "appSettings.Development.json"(for environment variable is Development), "appSettings.Stage.json"(for environment variable is Stage), "appSettings.Production.json"(for environment variable is Production) along with the "appSetting.json". Create A Sample .Net Core Application: Now for better understanding let's walk through with a sample .Net Core Web API application. The application can be created either by using Visual Studio 2019(VS Editor supports .Net Core Version 3.0plus) or visual Studio Code App Loads appSettings.json And appSettings.{Environmental_Variable}.json By Default: On application start, appSettings.json and ap