⌘ K
dart · flutter · brace indent · live

Format Dart and Flutter code

A brace-tracking indenter for Dart. Handles widget trees, async functions, and class bodies. Use `dart format` for production. Runs locally.

Dart Formatter
Input
54 B
1 lines
Output
55 B
2 lines
Status
ready
live
Ratio
1.02×
out/in
input · dart
output · formatted dart
void main(){final name='World';print('Hello, $name');}
Quick Start

How to format Dart

Tracks brace and bracket depth across Flutter widget trees, async functions, and class declarations.

  1. 01

    Paste Dart source

    Widget code, model classes, and async helpers all flow through.

    Parsing runs through Prettier’s standalone bundle (or the language-specific equivalent) loaded lazily — no parser ships until the tool is opened.

    dartPrettierASTstandalonelazy
    input · sourceraw · AST
    void main(){print('hi');}
    loaded · parsedAST · ready
  2. 02

    Pick indent width

    2 spaces is the official Dart style; 4 is also common.

    Indent width, tab style, and print-width re-format through a memoised pass — switching 2 → 4 spaces never re-parses, only re-prints.

    optionsindentprint-widthmemoisedlive
    opts · optionsindent · live
    indent=2
    options applied · livelive
  3. 03

    Watch widgets align

    Each nested widget constructor and method body indents one level deeper per brace.

    The formatter is deterministic and idempotent: running it twice produces byte-identical output, which keeps diffs and git noise to a minimum.

    liveidempotentdeterministicdiff-cleanstable
    out · formattedindented · ready
    void main() {
  print('hi');
}
    formatted · liveidempotent
  4. 04

    Copy or download

    Export as .dart or copy. Source stays in your browser.

    Download writes a Blob with the language-appropriate extension; copy uses navigator.clipboard.writeText so the output preserves all whitespace exactly.

    exportclipboardbloblanguage MIMEclient-side
    ok · copiedready · done
    ✓ Copied
    shipped · ready to shipsuccess
Pro tips

Formatting tips that keep diffs sane

Pick one config and pin it

Inconsistent formatting causes diff churn. Commit .prettierrc / .editorconfig and enforce in CI.

Format on save

Editor integration is faster feedback than a pre-commit hook. Use both for belt-and-braces.

Idempotency matters

Running the formatter twice should produce identical output. Test this on a representative file.

Match the language community

Default to community conventions: 2 spaces for JS/CSS, 4 for Python, tabs for Go. Fights over indent are a productivity tax.

Print-width drives wrapping

80, 100, and 120 are the common targets. Wider lines parse fast but review slower side-by-side.

Don’t mix formatters and linters

Prettier handles whitespace; ESLint handles correctness. Disable overlapping rules to avoid fight-club configs.

Related toolsKotlin FormatterSwift FormatterJava FormatterC# FormatterJS FormatterTS Formatter
Use Cases

When to format Dart

Flutter snippets, AI output, gist cleanup.

Flutter widgets

Re-indent a compressed widget tree pasted from a tutorial. Idempotent: running the formatter twice produces byte-identical output, which is the foundation of a clean CI gate. Pair with a pre-commit hook so PRs arrive already formatted, focusing review on logic.

idempotent

AI output

Clean up Dart emitted by code-gen assistants. Pairs with EditorConfig + .prettierrc for end-to-end consistency. Whitespace-only changes vanish so reviewers see real diffs, and git blame stays honest about who wrote what.

CI-ready

Gist cleanup

Make samples from DartPad and gists readable. Output respects your indent width, tab style, and print-width — settings carry over for repeat runs. Switching 2-space to 4-space costs nothing in CPU but standardises an entire codebase.

diff-clean

Code review

Strip whitespace churn so diffs show real changes. Format-on-save is the fastest feedback loop; CI is the safety net. Together they make inconsistent indentation a thing of the past and free up review cycles for genuine concerns.

PR-friendly

Quick fix

Reformat without spinning up dart format. Whitespace-only changes don't trigger downstream content-hash invalidations, so CDN cache keys and CI cache layers stay warm. Real changes get all the rebuild budget.

review-ready

Docs examples

Standardise Dart examples for blog and docs. Pairs with linters (ESLint, Stylelint, pylint) that catch what formatting alone can't — bugs, unused imports, dead code. Each tool stays in its lane, and the codebase stays clean.

deterministic
FAQ

Frequently asked questions

No — it's a heuristic indenter. Run `dart format` for the canonical Dart style.
Trailing commas are preserved as written; depth comes from brace counts only.
Async function bodies indent based on surrounding brace context like any block.
No — single and double-quoted strings are scanned and skipped.
No — the formatter runs locally in your browser tab.
Suggest a tool

Something missing?

Tell us what you need. We ship the top requests every two weeks.

Sent straight to the maintainers · no account needed
47 in queue·8 shipped this month
Request queued. Thanks!