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 macOS is available at:
http://127.0.0.1:52129/QjqebSY4lQ8=/
The Flutter DevTools debugger and profiler on macOS is available at:
http://127.0.0.1:9100?uri=http://127.0.0.1:52129/QjqebSY4lQ8=/

Open the DevTools instance connected to your app by opening the second link in Chrome.

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 again with the new URL.

Connect to a new app instance

If your app stops running or you opened DevTools manually, you should see a Connect dialog:

You can manually connect DevTools to a new app instance by copying the Observatory link you got from running your app, such as http://127.0.0.1:52129/QjqebSY4lQ8=/ and pasting it into the connect dialog: