Last updated: March 2026
What Is Code Diff?
Code diff is the process of comparing two versions of source code to identify what changed. This tool uses the Myers diff algorithm (the same algorithm behind git diff) to compute the minimum set of changes between your original and modified code, then displays them with clear visual highlighting.
Whether you are reviewing a pull request, debugging a regression, or comparing two implementations, a good diff tool helps you understand changes quickly and accurately. Character-level highlighting ensures you never miss a subtle change buried in a long line of code.
How to Use This Tool
- Paste your original code in the left panel and the modified version in the right panel.
- Review the diff output below. Added lines appear in green, removed lines in red, and modified lines in yellow with character-level highlights.
- Switch between views. Side-by-side for detailed review, unified for a compact git-style view.
- Use navigation to jump between changes with the arrow buttons or N/P keyboard shortcuts.
- Export your results as unified diff, .patch file, CSV, or JSON.
Common Use Cases for Code Diff
Code reviews: Before merging a branch, paste the before and after versions to review exactly what changed. The character-level diff catches subtle changes that are easy to miss in a full file read-through.
Debugging regressions: When something breaks after a deploy, compare the last known working version with the current version to identify the change that caused the issue.
Comparing implementations: When evaluating two different approaches to solving the same problem, paste both versions to see exactly how they differ in structure and logic.
Migration verification: After migrating code to a new framework or language version, compare the original and migrated code to ensure nothing was lost or incorrectly translated.
Frequently Asked Questions
How is this different from a text diff tool?
A code diff tool is built specifically for source code. It provides syntax highlighting for 20+ programming languages, character-level diff within modified lines, and exports in standard formats like unified diff and .patch files. Plain text diff tools lack these code-specific features.
What programming languages are supported?
Syntax highlighting is available for JavaScript, TypeScript, Python, HTML, CSS, JSON, SQL, Java, C, C++, C#, Go, Rust, Ruby, PHP, Swift, Kotlin, Shell/Bash, YAML, XML, and Markdown. The language is auto-detected or can be set manually.
Can I export the diff as a patch file?
Yes. You can copy the unified diff to your clipboard, download it as a .patch file compatible with git apply, or export the full results as CSV or structured JSON.
Is my code safe?
All processing happens in your browser. Your code is never sent to any server, stored, or logged. This tool is safe for proprietary code, client projects, and any sensitive source files.
What is the Myers diff algorithm?
The Myers diff algorithm is the same algorithm used by git to compute differences between files. It finds the minimum number of edits (insertions and deletions) needed to transform one file into another, producing clean, readable diffs.