DartPad

DartPad (dartpad.dartlang.org) is an open-source tool that lets you play with the Dart language in any modern browser. Here’s what DartPad looks like:

DartPad Hello World

Library support

DartPad supports dart:* libraries that work with web apps; it doesn’t support dart:io or libraries from packages. If you want to use dart:io, use the Dart SDK instead. If you want to use a package, get the SDK for a platform that the package supports.

Getting started

To get familiar with DartPad, try these steps:

Open DartPad, and run some samples

  1. Go to dartpad.dartlang.org.

    A sample appears on the left and the output appears on the right. If you’ve played with DartPad before, you can click New Pad to get back to the original sample.

  2. Click Run.

    The sample runs again, updating the output.

  3. Choose an HTML sample, using the Samples list at the upper right.

    For example, choose Hello World HTML. Again, the output appears to the right. By default, you see the HTML output—what you’d see in a browser.

  4. Click CONSOLE to view the sample’s console output.

  5. On the left, click the HTML tab to view the sample’s HTML markup.

Create a command-line app

To create a simple command-line app, use New Pad.

  1. Click the New Pad button.

    The source code for the Hello World app appears under the DART tab.

  2. Change the code. For example, change the main() function to contain this code:

    for (var char in 'hello'.split('')) {
      print(char);
    }

    As you type, DartPad shows hints, documentation, and autocomplete suggestions.

  3. Click the Format button. DartPad uses the Dart formatter to ensure that your code has proper indentation, white space, and line wrapping.

  4. Run your app.

  5. If you didn’t happen to have any bugs while you were entering the code, try introducing a bug.

    For example, if you change split to spit, you get warnings at the bottom of the window and in the Run button. If you run the app, you’ll see output from an uncaught exception.

Create a web app

To create a simple web app, start with the Hello World HTML sample.

  1. Click Samples, and choose Hello World HTML. If you've already edited Hello World HTML, click Reset to restore the original version.
  2. Edit the HTML:
    1. Click HTML to view the HTML code.
    2. Change the text inside the h2 element from Hello world to something else—perhaps Hola mundo.

    The display under HTML OUTPUT updates as you type.

  3. Edit the Dart code:
    1. Click DART to view the Dart code.
    2. Change the value displayed by count.text. For example, change '${i}' to '#${i}'.
    3. Click Run to compile and run the Dart code, updating the HTML OUTPUT display.

Checking Dart version info

DartPad’s various language features and APIs depend on the Dart SDK version that DartPad is based on, to view the version number firstly go to the Dart editor.

  1. Click the DartPad title, which is at the upper left of your DartPad editor.
  2. At the bottom of the dialog that appears, you can see the Dart SDK version number.

For example, if DartPad is based on Dart SDK 1.25.0, then DartPad partially supports type safety but doesn’t support many other Dart 2 features.