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Diff Checker

Compare two texts side-by-side and see additions, deletions, and changes highlighted

How to Use

1. Paste your original text in the left textarea

2. Paste the modified version in the right textarea

3. Differences are highlighted automatically:

  • Green = Added lines
  • Red = Removed lines
  • No highlight = Unchanged lines

All comparisons happen in your browser. Your data is never sent to any server.

About Diff Checker

Diff Checker is a free online tool for comparing two text files or code snippets to identify differences with clear visual highlighting. Whether you're a developer reviewing code changes, a writer comparing document versions, a student checking essay revisions, or anyone needing to spot differences between texts, this tool provides instant line-by-line comparison with professional diff output. The tool offers two viewing modes: side-by-side view shows both texts in parallel columns with aligned lines, making it easy to compare corresponding sections; unified view presents changes in a single column similar to Git diff output, with context lines showing where changes occur. Additions are highlighted in green, deletions in red, and unchanged lines in neutral colors. Line numbers are displayed for easy reference when discussing specific changes. The statistics panel shows total lines added, removed, and unchanged at a glance. Convenient buttons let you swap the original and modified texts or clear both inputs to start fresh. The diff algorithm uses the Longest Common Subsequence (LCS) approach, the same algorithm used by professional diff tools, ensuring accurate identification of the minimal set of changes needed to transform one text into another. All processing happens entirely in your browser using JavaScript, ensuring complete privacy—your texts never leave your device or get sent to any server. Common use cases include comparing code before and after refactoring, reviewing document revisions, checking configuration file changes, verifying data transformations, comparing log outputs, finding differences in API responses, and debugging by comparing expected vs actual output. The tool handles edge cases including identical texts (showing 'no differences'), completely different texts, empty inputs, and large files efficiently. Works on all modern browsers with no registration or installation required.
Key Features
What makes our diff checker the best choice
  • ✓100% free to use, no registration required
  • ✓All processing happens in your browser - complete privacy
  • ✓Instant results with real-time updates
  • ✓Works offline once loaded
  • ✓Mobile-friendly and responsive design

Frequently Asked Questions

Is this diff checker completely free?

Yes! This tool is 100% free to use with no hidden costs, registration requirements, or usage limits.

Is my data secure?

Absolutely. All processing happens entirely in your browser using JavaScript. Your data never leaves your device or gets sent to any server, ensuring complete privacy and security.

Do I need to create an account?

No account needed! Simply visit this page and start using the tool immediately. We believe in keeping things simple and accessible.

Does it work offline?

Once the page is loaded, the tool works completely offline since all processing happens in your browser. No internet connection is required for the tool to function.

Are these tools suitable for production use?

Yes, all developer tools use standard algorithms and produce reliable output suitable for development and production workflows. The outputs are identical to what you'd get from command-line tools.

Can I integrate these tools into my workflow?

While these are browser-based tools, you can easily copy outputs for use in your projects. For automation, consider using equivalent command-line tools or libraries in your preferred programming language.

Are the conversions and encodings reversible?

Most conversions like Base64, URL encoding, and JSON formatting are fully reversible. Some operations like hashing are one-way by design and cannot be reversed.

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