Dart DevTools

Dart DevTools is a suite of debugging and performance tools for Dart and Flutter.

Using DevTools with a Flutter app

For details on using DevTools with a Flutter app, see the Flutter DevTools documentation.

Using DevTools with a command-line app

You can use DevTools to perform source-level debugging or to view general log and diagnostics information for a running command-line app.

1. Install DevTools

Use pub to install or update DevTools:

$ pub global activate devtools

2. Launch the DevTools server

Once you have DevTools, use the devtools command to run the local web server for DevTools:

$ pub global run devtools
Serving DevTools at

3. Start the target app

Use the dart --observe command to execute the main file for the Dart command-line app that you want to debug or observe:

$ cd path/to/dart/app
$ dart --observe main.dart

Observatory listening on

Note the “listening” URL. You’ll need this URL in the next step.

4. Open DevTools and connect to the target app

  1. Open Chrome browser window and navigate to http://localhost:9100.
  2. Paste the “listening” URL into the text field under Connect to a running app, and click the Connect button.

DevTools connection dialog