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C Code Formatter

Format C and C++ with clang-format compiled to WebAssembly, using the LLVM style. Preprocessor directives, comments, string literals and pointer declarations are handled by the real engine, not by pattern matching.

Programming Language Tools

How to use C Code Formatter

  1. Paste C or C++ source into the input panel.
  2. Choose 2 spaces, 4 spaces or tabs.
  3. Press Format. clang-format loads on first use, then runs instantly.
  4. Copy the result or download it as formatted.c.

Examples

Before

Everything crammed onto as few lines as possible.

int main(int argc,char**argv){
if(argc>1){printf("%s\n",argv[1]);}
return 0;}

After

LLVM style: braces, indentation and spacing normalised.

int main(int argc, char **argv) {
  if (argc > 1) {
      printf("%s\n", argv[1]);
  }
  return 0;
}

Features

  • The real clang-format, compiled to WebAssembly and running locally
  • LLVM base style with a 100-column limit
  • 2-space, 4-space or tab indentation
  • Correct handling of #include, #define and conditional compilation
  • Comments, string literals and character constants are preserved exactly
  • Pointer and reference alignment, brace placement and continuation indents
  • Copy to clipboard or download formatted.c
  • The engine downloads only when you press Format

Frequently asked questions

Which formatter is this?
clang-format, the formatter shipped with LLVM and used across the C and C++ world, compiled to WebAssembly so it runs in your browser.
Does it work on C++ too?
Yes. clang-format handles C, C++, and Objective-C with the same engine, so templates, namespaces and classes are formatted correctly.
Which style does it use?
The LLVM base style with a 100-column limit, and your chosen indentation applied on top. LLVM is the clang-format default and a reasonable neutral choice.
Will it reformat my macros?
Preprocessor directives are understood and indented sensibly rather than treated as ordinary lines. Very unusual macro constructions can still confuse any formatter, clang-format included.
Does it compile or check my code?
No. It formats. clang-format works on a token stream and does not need the code to compile, which is why it can tidy a fragment as happily as a full file.
Is my source uploaded?
No. The WebAssembly module runs in your browser and your code never leaves the tab.

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About C Code Formatter

C Code Formatter is part of Programming Language Tools on ToolHive, a growing collection of small, focused utilities for developers, designers and students. Formatters and playgrounds for Python, C, Java, Go, Rust and SQL. Everything runs client-side, so your data never leaves the browser tab — which makes these tools safe to use with work-in-progress code and private content.