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Check unused code

Checks unused classes, functions, top level variables, extensions, enums, mixins and type aliases.

Note: current implementation doesn't check for particular class methods usage. Also, it treats code, that is imported with not named conditional imports as unused. This will be fixed in the future releases.

To execute the command, run

$ dart run dart_code_metrics:metrics check-unused-code lib

# or for a Flutter package
$ flutter pub run dart_code_metrics:metrics check-unused-code lib

Full command description:

Usage: metrics check-unused-code [arguments] <directories>
-h, --help Print this usage information.

-r, --reporter=<console> The format of the output of the analysis.
[console (default), json]
--report-to-file=<path/to/report.json> The path, where a JSON file with the analysis result will be placed (only for the JSON reporter).

-c, --print-config Print resolved config.

--root-folder=<./> Root folder.
(defaults to current directory)
--sdk-path=<directory-path> Dart SDK directory path.
Should be provided only when you run the application as compiled executable( and automatic Dart SDK path detection fails.
--exclude=<{/**.g.dart,/**.freezed.dart}> File paths in Glob syntax to be exclude.
(defaults to "{/**.g.dart,/**.freezed.dart}")

--no-congratulate Don't show output even when there are no issues.

--[no-]monorepo Treat all exported code as unused by default.

--[no-]fatal-unused Treat find unused file as fatal.

Suppressing the command

In order to suppress the command add the ignore: unused-code comment. To suppress for an entire file add ignore_for_file: unused-code to the beginning of a file.

Monorepo support

By default the command treats all code that is exported from the package as used. To disable this behavior use --monorepo flag. This might be useful when all the packages in your repository are only used within the repository and are not published to the pub.

Output example


Use --reporter=console to enable this format.



The reporter prints a single JSON object containing meta information and the unused code file paths. Use --reporter=json to enable this format.

The root object fields are

  • formatVersion - an integer representing the format version (will be incremented each time the serialization format changes)
  • timestamp - a creation time of the report in YYYY-MM-DD HH:MM:SS format
  • unusedCode - an array of unused code issues
"formatVersion": 2,
"timestamp": "2021-04-11 14:44:42",
"unusedCode": [

The unusedCode object fields are

  • path - a relative path of the unused file
  • issues - an array of issues detected in the target file
"path": "lib/src/some/file.dart",
"issues": [

The issue object fields are

  • declarationType - unused declaration type
  • declarationName - unused declaration name
  • offset - a zero-based offset of the class member location in the source
  • line - a zero-based line of the class member location in the source
  • column - a zero-based column of class member the location in the source
"declarationType": "extension",
"declarationName": "StringX",
"offset": 156,
"line": 7,
"column": 1