Install and run DevTools from the command line

To run Dart DevTools from the CLI, you must have dart on your path. Then you can run the following command to launch DevTools:

dart devtools

To upgrade DevTools, upgrade your Dart SDK. If a newer Dart SDK includes a newer version of DevTools, dart devtools will automatically launch this version. If which dart points to the Dart SDK included in your Flutter SDK, then DevTools will be upgraded when you upgrade your Flutter SDK to a newer version.

When you run DevTools from the command line, you should see output that looks something like:

Serving DevTools at http://127.0.0.1:9100

Start an application to debug

Next, start an app to connect to. This can be either a Flutter application or a Dart command-line application. The command below specifies a Flutter app:

cd path/to/flutter/app
flutter run

You need to have a device connected, or a simulator open, for flutter run to work. Once the app starts, you’ll see a message in your terminal that looks like the following:

An Observatory debugger and profiler on iPhone X is available
at: http://127.0.0.1:50976/Swm0bjIe0ks=/

Keep note of this URL, as you will use it to connect your app to DevTools.

Open DevTools and connect to the target app

Once it’s set up, using DevTools is as simple as opening a Chrome browser window and navigating to http://localhost:9100.

Once DevTools opens, you should see a connect dialog:

Screenshot of a logging view

Paste the URL you got from running your app (in this example, http://127.0.0.1:50976/Swm0bjIe0ks=/) into the connect dialog to connect your app to DevTools.

This URL contains a security token, so it’s different for each run of your app. This means that if you stop your application and re-run it, you need to connect to DevTools with the new URL.