Online C Code Formatter & Beautifier — Free Tool

What is the Online C Code Formatter?

The C Code Formatter is a free browser-based tool that formats, indents, and structures unorganized C source code into clean, readable code according to industry-standard indentation conventions.

Whether you are preparing code for academic lab submissions, reviewing code in team pull requests, or tidying up complex nested control flow, this tool applies standardized spacing, brace placement, and indentation rules instantly.

c (ISO Standard)
Run in Compiler.cCopy
#include <stdio.h>

int main() {
    int numbers[] = {5, 2, 8, 1, 9};
    int n = 5;

    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (numbers[j] > numbers[j + 1]) {
                int temp = numbers[j];
                numbers[j] = numbers[j + 1];
                numbers[j + 1] = temp;
            }
        }
    }

    printf("Sorted array:\n");
    for (int i = 0; i < n; i++) {
        printf("%d ", numbers[i]);
    }
    printf("\n");

    return 0;
}

Supported Formatting Styles

1. K&R Style (Kernighan & Ritchie)

The classic style used throughout the C programming specification and UNIX systems. Opening braces for functions begin on a new line, whereas control statements (if, for, while) keep the opening brace on the same line:

c (ISO Standard)
Run in Compiler.cCopy
void process_item(int id) {
    if (id > 0) {
        printf("Valid ID: %d\n", id);
    } else {
        printf("Invalid ID\n");
    }
}

2. Allman Style (BSD)

Widely popular in systems development and academic environments. Opening and closing braces are aligned on their own separate lines, making block boundaries visually distinct:

c (ISO Standard)
Run in Compiler.cCopy
void process_item(int id)
{
    if (id > 0)
    {
        printf("Valid ID: %d\n", id);
    }
    else
    {
        printf("Invalid ID\n");
    }
}

3. GNU Style

Standardized across the GNU project toolchain with 2-space indentation levels and braces indented between control statements:

c (ISO Standard)
Run in Compiler.cCopy
void process_item(int id)
{
  if (id > 0)
    {
      printf("Valid ID: %d\n", id);
    }
}

Why Format Your C Code?

1. Bug Prevention: Misaligned indentation is one of the most common causes of logic bugs when working with single-statement loops and conditionals.
2. Team Consistency: Enforces a uniform styling standard across multi-developer repositories.
3. Academic Evaluation: Clean, formatted code receives better reviews during university grading and technical interview assessments.

Related Developer Tools

• Step through your code execution visually with our Online C Debugger.
• Catch syntax mistakes before compiling with the C Syntax Checker.
• Brush up on core language rules in our C Programming Basics Tutorial.