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rust · indent · brace-tracking · live

Format Rust source

Basic indenter for Rust — tracks {, [, ( depth and normalises whitespace. Use rustfmt for production formatting. Runs locally.

Rust Formatter
Input
53 B
1 lines
Output
54 B
2 lines
Status
ready
live
Ratio
1.02×
out/in
input · rust
output · formatted rust
fn main(){let s=String::from("hi");println!("{}",s);}
Quick Start

How to format Rust

A brace-tracking indenter — counts {, [, ( open/close to lay out fn/impl/match blocks consistently.

  1. 01

    Paste source

    A function, an impl block, or a small crate fragment.

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

    rustPrettierASTstandalonelazy
    input · sourceraw · AST
    fn f(){1}
    loaded · parsedAST · ready
  2. 02

    Set indent width

    4 spaces is the rustfmt default. Tabs are not produced — spaces only.

    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=4
    options applied · livelive
  3. 03

    Watch blocks align

    Braces open new indent levels, closers dedent. Strings, char literals and // comments are skipped.

    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
    fn f() {
    1
}
    formatted · liveidempotent
  4. 04

    Copy or download

    Save as .rs or copy to clipboard. 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
    OK 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 toolsGo FormatterC FormatterC++ FormatterJava FormatterSwift FormatterKotlin Formatter
Use Cases

When to format Rust

Snippet cleanup, code reviews, docs examples.

Snippet cleanup

Tidy a tutorial paste before saving to a crate. 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

Code reviews

Normalise whitespace so diffs show real changes. 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

Macro output

Re-indent expanded macros for inspection. 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

Quick edits

Reformat after an inline change. 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

Playground saves

Tidy code copied from the Rust playground. 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 Rust examples for documentation. 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 is a brace-tracking indenter, not the official formatter.
No. Brace position is preserved; only indentation changes.
No — lifetimes look like ordinary tokens to the indenter. They are passed through unchanged.
#[derive(...)] and other attributes stay on their own lines as authored.
No — the formatter runs locally in your browser tab.
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