Build Status

What is this?

This is a companion repo to the main Flutter repo. It contains the source code for a suite of performance tools for Dart and Flutter.

Trying it out


Currently, the best way to try DevTools out is by running it as a pub globally activated package.

If you have pub on your path, you can run:

  • pub global activate devtools

If you have flutter on your path, you can run:

  • flutter packages pub global activate devtools

That will install (or update) DevTools on your machine.

Going forward, we expect to have additional (and easier!) distributions mechanisms for DevTools.

Run the DevTools application server

Next, run the local web server, which will serve the DevTools application itself.

Run one of the following two commands:

  • pub global run devtools (if you have pub on your path)

  • flutter packages pub global run devtools (if you have flutter on your path)

On the command-line, you should see output that looks something like:

Serving DevTools at

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 example below uses a Flutter app.

  • cd path/to/flutter/app
  • and, run flutter run --observatory-port=9200

You'll need to have a device connected or a simulator open for flutter run to work. Once the app starts up, you'll be able to connect to it from devtools.

Open DevTools and connect to the target app

Using DevTools now is as simple as opening a local browser window and pointing the DevTools app to the running Flutter application. If you used the same ports as the example above, you can open:


This can also be done via the command line with open http://localhost:9100/?port=9200. The first port in the url is for the local server that is serving the DevTools web UI. The second port is to tell DevTools itself which local app to connect to for debugging and inspection.


Feedback and issues are best reported at Thanks for trying out DevTools!