Code Diff Checker

What Is a Code Diff?

A diff (short for "difference") is a comparison between two text blocks that highlights what was added, removed, or changed. Diff algorithms are fundamental to version control systems like Git, code review platforms, and merge tools.

The concept originated with the Unix diff command created in the 1970s. Today, diff tools use sophisticated algorithms (like Myers' algorithm or patience diff) to produce the most readable comparison of two files.

How to Use This Tool

1. Paste the original code into the left text area.
2. Paste the modified code into the right text area.
3. Click Compare to see a line-by-line diff with additions and deletions highlighted.

Common Use Cases

• Code Review: Compare a pull request's changes to understand what a teammate modified.
• Debugging: Find exactly which lines changed between a working version and a broken version.
• Configuration Auditing: Compare two config files to spot differences in server settings.
• Database Schema Comparison: Diff two SQL schema exports to identify structural changes.
• Document Comparison: Compare two versions of any plain-text document.

Understanding Diff Output

Diff results typically use these conventions:

• + Added lines — Lines present in Code 2 but not in Code 1.
• - Removed lines — Lines present in Code 1 but not in Code 2.
• Unchanged lines — Lines that are identical in both blocks (shown for context).

For plain text comparison, try our Text Diff Checker.

Why Use This Tool?

• Instantly spot differences between two code blocks.
• Color-coded additions, deletions, and modifications.
• Perfect for code reviews and comparing versions.
• Runs entirely in your browser — your code stays private.

Frequently Asked Questions