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ASP.NET Core: Use Keys Stored in appsettings.json in .NET 6

Modify and use appsettings.json keys in ASP.NET Core for custom settings; also, create and use custom JSON files for use in C# web apps.

This article requires .NET 6.

In .NET 6, it was made easy to use the custom keys in appsettings.json. The WebApplicationBuilder has a configuration object as a property that can be used.

Modify the appsettings.json as in this example.

  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
  "AllowedHosts": "*",
  "MyCustomKey": "Some string value..."

Modify the Program.cs as in this example snippet.

var builder = WebApplication.CreateBuilder(args);
// ...

string myCustomKey = builder.Configuration["MyCustomKey"]; // NOTE: do something with myCustomKey

Alternate/Custom JSON Configuration Files

Also, import custom JSON configuration files to use. Create custom.json as follows.

  "Custom": {
    "Level": {
      "Default": "1"

To use the above JSON settings file:

IConfiguration config = new ConfigurationBuilder().AddJsonFile("custom.json").Build(); // NOTE: custom.json should be in the same folder as Program.cs

string myCustomLevelDefault = config["Custom:Level:Default"]; // NOTE: do something with myCustomLevelDefault, which equals "1"

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