Code Diff Checker
Compare code differences with syntax highlighting
Compare versions
Paste both versions and compare. Your code stays on this device.
Differences
- Total lines
- 0
- Added
- 0
- Removed
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- Modified
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Compare code to see additions, deletions and modifications.
Free Online Code Diff Checker & Comparison Tool
Our code diff checker lets you compare two blocks of text or source code side by side and see every addition, deletion, and modification. Paste the old and new version of a function before approving a pull request, or two nginx configs after a deploy broke something, and this online diff tool highlights differences with clear color coding so nothing slips through.
The tool offers two viewing modes -- side-by-side and unified diff -- giving you flexibility depending on your workflow. Side-by-side mode mirrors the experience of professional code review tools, while unified mode condenses changes into a single scrollable view that is easy to scan. Both modes include line numbers and change-type indicators for precise navigation.
Your code is never uploaded and never leaves your machine, making this diff comparison tool safe for proprietary codebases, private repositories, and sensitive configuration files. Copy the diff output to share results with teammates or paste into documentation.
Key Features
- Side-by-side and unified diff viewing modes
- Color-coded highlighting for additions, deletions, and modifications
- Line-by-line comparison with numbered output
- Real-time statistics showing total, added, removed, and modified line counts
- Works with any programming language or plain text
- One-click copy of the complete diff output
- Sample code loader for quick demonstrations
- Visual legend explaining color codes for each change type
- Responsive layout that works on desktop and mobile
- Your code is never uploaded, so it stays private
How to Use the Diff Checker
- Paste original code: Enter or paste the original version of your code into the left text area labeled "Original Code."
- Paste modified code: Enter or paste the updated version into the right text area labeled "Modified Code."
- Click Compare: Press the "Compare Code" button to generate the diff analysis.
- Choose a view mode: Switch between "Side by Side" and "Unified View" using the dropdown selector to find the layout that suits you best.
- Review differences: Examine the color-coded output -- green for added lines, red for removed lines, and yellow for modified lines.
- Copy or share: Click "Copy Diff" to place the diff text on your clipboard for pasting into reviews, tickets, or documentation.
Use Cases
- Code review: Compare original and modified code to understand exactly what changed before approving a merge request.
- Debugging regressions: Paste a working version and a broken version to pinpoint the lines that introduced a bug.
- Configuration auditing: Diff server configs, environment files, or YAML manifests to verify deployment changes.
- Documentation updates: Compare documentation drafts to ensure all edits are intentional and accurate.
- Learning from examples: Place a starter template alongside a completed solution to visualize what was added or changed.
- Version control validation: Verify that local file changes match the expected differences before committing.
Frequently Asked Questions
Does it support all programming languages?
The diff checker compares text line by line, so it works with any programming language, markup format, or plain text. There is no language-specific parsing required.
What is the difference between side-by-side and unified view?
Side-by-side mode shows the original and modified code in two parallel panels for direct visual comparison. Unified view merges both into a single panel, displaying additions and deletions inline -- similar to the output of the "git diff" command.
Can I compare files instead of pasting text?
Currently the tool accepts pasted text. To compare files, simply open them in a text editor, copy the contents, and paste them into the original and modified input areas.
Tips & Best Practices
- Normalize formatting first: Beautify both code blocks with consistent indentation before comparing to avoid noise from whitespace differences.
- Use the sample loader: Click "Load Sample" to see the tool in action before pasting your own code.
- Check the stats bar: Review the added, removed, and modified counts at the top for a quick summary before diving into details.
- Switch view modes: Start with side-by-side for structural changes, then switch to unified for a compact summary you can paste into a ticket.
- Copy diff for documentation: Use the "Copy Diff" button to grab a plain-text diff that can be pasted into code review comments or changelogs.