⌘ K
c · brace indent · live · client-side

Format C source files

A brace-tracking indenter for C code. Normalises whitespace and re-indents nested blocks. Use clang-format for production. Runs locally.

C Formatter
Input
65 B
2 lines
Output
66 B
3 lines
Status
ready
live
Ratio
1.02×
out/in
input · c
output · formatted c
#include <stdio.h>
int main(){printf("Hello, World\n");return 0;}
Quick Start

How to format C

A brace-aware indenter — tracks [ ] ( ) depth and re-pads each line. Strings and line comments are respected.

  1. 01

    Paste C source

    Function bodies, struct declarations, and macros all work.

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

    cPrettierASTstandalonelazy
    input · sourceraw · AST
    int main(){return 0;}
    loaded · parsedAST · ready
  2. 02

    Pick indent width

    4 spaces is the GNU default; 2 and 8 are 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=4
    options applied · livelive
  3. 03

    Watch blocks align

    Each open brace bumps depth; the closing brace pulls back to match.

    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
    int main() {
    return 0;
}
    formatted · liveidempotent
  4. 04

    Copy or download

    Export as .c or .h, 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
    ✓ 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&rsquo;t mix formatters and linters

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

Related toolsC++ FormatterC# FormatterRust FormatterJava FormatterKotlin FormatterDart Formatter
Use Cases

When to format C

Kernel patches, embedded code, learning.

Patch prep

Tidy whitespace before sending to lkml or a code review. 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

Embedded code

Re-indent vendor SDK snippets and hardware drivers. 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

Learning C

Make minified textbook examples 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 only 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

Snippet cleanup

Reformat one-liners pasted from articles. 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 C examples in technical 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's a brace-tracking indenter. Run clang-format for real semantic formatting.
#include and #define lines are not specially handled; they just respect outer brace depth.
Trailing backslash continuations are not joined; lines indent based on brace context only.
No — quoted strings are scanned and ignored when counting braces.
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!