How to suppress dotnet whatch run to open a browser

An interesting question on Twitter leads me to write this small post. The question was how to suppress opening a browser when you run dotnet watch run.

The thing is, that you might not want to open a browser if you run dotnet watch run on an Web API project. Since the Web API projects have Swagger enabled by default, this might make sense but often you just want to run your backend project while your frontend project is open in a browser or whatever frontend you have.

Using an environment variable

There are two options to change that behavior. You can set an environment variable, which sets the behavior globally or in a console session:

SET DOTNET_WATCH_SUPPRESS_LAUNCH_BROWSER=1

This will override the default behavior.

Using the launchSettings.json

The better option is to change it project-wise for all the projects you want to suppress. This can be done in the launchSettings.json that you will find in the Properties folder of each project. The launchsettings.json contains iisSettings and two or more profiles that configures how the applications will be launched:

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:32265",
      "sslPort": 44369
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "swagger",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "MyProject": {
      "commandName": "Project",
      "dotnetRunMessages": "true",
      "launchBrowser": true, 
      "launchUrl": "swagger",
      "applicationUrl": "https://localhost:5001;http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

The launchBrowser property in the profiles defines whether the browser should be opened or not. Set it to false in case you want to suppress it.

In case you set the environment variable, it will override the setting of the launchsettings.json.

Conclusion

In many cases you might want to see the Swagger UI in your browser to test your API but there are cases as well, where you just want to spin up up your backend and to work on your front end using the running API.

If you found any error on this post, feel free to tell me: Add a comment below, file an issue on GitHub or edit this page on GitHub and send me an PullRequest.

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Jürgen Gutsch Jürgen Gutsch
@sharpcms
.NET junkie, addicted to web and software development, clean coder, MVP for Developer Technologies