home/dev/code-diff

Free Online Code Diff Tool with Syntax Highlighting

Compare code side by side with syntax highlighting

How to Use Code Diff

  1. 1

    Paste original code

    Enter the original code in the left panel.

  2. 2

    Paste modified code

    Enter the modified version in the right panel.

  3. 3

    Review differences

    Added, removed, and changed lines are highlighted with syntax coloring.

Frequently Asked Questions

Is my data safe?
Yes. All processing happens entirely in your browser. Your data never leaves your device and is never uploaded to any server.
What languages are supported?
Syntax highlighting supports JavaScript, TypeScript, Python, Java, Go, Rust, C/C++, HTML, CSS, JSON, YAML, SQL, and many more.
How is this different from the Text Diff tool?
The Code Diff tool adds syntax highlighting and is optimized for source code. The Text Diff tool is better for plain text comparisons like documents or logs.
Can I compare entire files?
Yes. Paste or type any amount of code in both panels. The tool handles files of any size, though very large files may be slower on mobile devices.
Does it detect moved lines?
The tool performs a line-by-line diff. Lines that are moved will show as deleted from the old position and added at the new position.

Learn more

About Code Diff

Compare two code files side by side with syntax highlighting and line-by-line diff detection. See additions, deletions, and modifications clearly highlighted. Supports all major programming languages. Perfect for code reviews, debugging, and tracking changes between versions. All processing happens in your browser — your code is never sent to any server.

Why Use Code Diff?
  • Syntax highlighting makes it easier to understand diffs in context, unlike plain text diff tools.
  • Side-by-side view shows exactly what changed between two versions of your code.
  • Supports all major programming languages with proper syntax coloring.
  • 100% client-side — safe for comparing proprietary or sensitive source code.
  • No installation needed — works instantly in any modern browser.
Common Use Cases

Code reviews

Compare the original and modified versions of a file to understand what changed during a code review.

Debugging regressions

Compare a working version of code with a broken version to pinpoint the exact change that introduced a bug.

Merge conflict resolution

Paste both sides of a merge conflict to understand the differences before deciding how to resolve them.

Version comparison

Compare configuration files, API responses, or data files between environments (staging vs production).

Tips & Best Practices
  • 💡Paste the older version on the left and the newer version on the right for conventional diff reading order.
  • 💡For large files, focus on the highlighted sections — unchanged code is dimmed to draw attention to the differences.
  • 💡Use this alongside the plain Text Diff tool when you do not need syntax highlighting and want a simpler view.
  • 💡When comparing minified code, run it through the JSON Formatter or a code formatter first to make the diff meaningful.
How It Works

The diff algorithm computes a line-by-line comparison using a longest common subsequence (LCS) approach, similar to the Unix diff command. Added lines are highlighted in green, removed lines in red, and modified lines show inline character-level changes. Syntax highlighting is applied using a lightweight tokenizer that supports JavaScript, TypeScript, Python, HTML, CSS, JSON, and other common languages.

More Developer Tools

{} JSON Formatter64 Base64🔑 JWT Decoder.* Regex Tester# Hash Generator% URL Encode/Decode& HTML EntitiesID UUID Generator⏱ Unix Timestamp01 Number Base📸 Code to Image📦 HTML/CSS/JS Minifier🌈 CSS Gradient Generator💠 Box Shadow Generator🪟 Glassmorphism Generator↔️ Flexbox Generator📊 CSS Grid Generator✂️ Clip-Path Generator

You might also like

± Text DiffText