Free Code Diff Checker Online
Compare code side-by-side or inline with syntax-aware highlighting. Supports JavaScript, Python, HTML, CSS, and JSON with word-level and character-level diff. 100% client-side — your code stays private.
How to Use the Code Diff Checker
- Paste your original code in the left textarea.
- Paste the modified code in the right textarea.
- Select the language for syntax-aware highlighting.
- Choose side-by-side or inline diff view.
- Toggle options: ignore whitespace and ignore blank lines.
- Click "Compare" to see the differences highlighted with line numbers.
Why Use This Code Diff Checker
Code review and debugging often require comparing two versions of a file. This tool makes it easy to spot additions, deletions, and changes with syntax-aware highlighting that understands your code structure.
With support for JavaScript, Python, HTML, CSS, and JSON, plus options like ignore whitespace and word-level diff, it's a complete solution for comparing code files.
Frequently Asked Questions
Side-by-side shows the original and modified code in two columns. Inline shows both versions in a single column with added/removed lines highlighted in place.
When enabled, differences in indentation, spaces, and tabs are ignored. Only actual code changes (adding, removing, or modifying text) are shown.
No. All diff computation happens entirely in your browser. Your code never leaves your device.
Unified diff is a standard text format that shows changes with +/- markers. It's commonly used in version control systems and patch files.
Use Cases
Pre-Merge Comparison
Compare code versions before merging branches to identify conflicts and ensure changes are correct before integration.
Config File Auditing
Audit configuration file changes to track modifications and ensure compliance with security and operational policies.
Pull Request Reviews
Review pull requests by comparing original and modified code with syntax-aware highlighting for efficient code reviews.
Unauthorized Modifications
Identify unauthorized code modifications by comparing expected and actual code versions for security audits.
Document Revisions
Track document revisions by comparing different versions of text files, configs, and code to maintain revision history.