Use this page to configure formatting options for Dart files. When you change these settings, the Preview pane shows how this will affect your code.
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The page is available only when the Dart plugin is installed and enabled on the Settings | Plugins page as described in Managing plugins.
In PhpStorm, Dart code is formatted using the dartfmt tool that has become an industry standard and is a part of the Dart SDK, see also the dart_style package documentation. The only configurable option is line length. By default, lines are 80 characters long. You can specify a custom value in the Line length field.