To update your code to follow the Dart formatting guidelines, use the dart format command. This formatting follows what you get when using an IDE or editor with Dart support.

Specify files to format


To reformat one or more Dart files, provide a list of paths to the desired files or directories.

Specify one path


Provide the path to one file or directory. If you specify a directory, dart format affects only the files in the immediate directory; it doesn't recurse through subdirectories.

Example: To format all the Dart files in or under the current directory:

$ dart format .

Specify multiple paths


To specify multiple files or directories, use a space-delimited list.

Example: To format all Dart files under the lib directory, plus one Dart file under the bin directory:

$ dart format lib bin/updater.dart

Prevent overwriting Dart files


By default, dart format overwrites the Dart files.

  • To not overwrite the files, add the --output or -o flag.
  • To get the contents of the formatted files, add -o show or -o json.
  • To see only which files would change, add -o none.
$ dart format -o show bin/my_app.dart

Notify when changes occur


To make dart format return an exit code when formatting changes occur, add the --set-exit-if-changed flag.

  • If changes occur, the dart format command returns an exit code of 1.
  • If changes don't occur, the dart format command returns an exit code of 0.

Use exit codes with continuous integration (CI) systems so they can trigger another action in response to the exit code.

$ dart format -o none --set-exit-if-changed bin/my_app.dart

Use trailing commas


Use optional trailing commas for better automatic formatting. Add a trailing comma at the end of parameter lists in functions, methods, and constructors. This helps the formatter insert the appropriate amount of line breaks for Dart-style code.

Affects whitespace only


To avoid making changes that might be unsafe, dart format only affects whitespace.

There's a lot more to writing readable and consistent code than just whitespace, though. To learn more about best practices for writing and styling Dart code, check out the Dart style guide.

Learn more


To learn about additional command-line options, use the dart help command or see the documentation for the dart_style package

$ dart help format