Text Diff Checker
Text Tools
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About This Tool
Free, private, serverless text diff checker. Compare two texts side by side with highlighted additions, deletions, and unchanged lines. Supports ignore whitespace and ignore case options. Color-coded diff output shows exactly what changed. LCS-based algorithm for accurate results. No data leaves your browser — 100% client-side comparison tool.
How to Use
- Paste your original text on the left and the modified text on the right.
- Click Compare to see the diff.
- Green lines are additions, red lines are deletions, and white lines are unchanged.
- Use Ignore whitespace or Ignore case for flexible comparison.
- Click Swap to switch the two texts.
Frequently Asked Questions
What algorithm does this tool use?
It uses the Longest Common Subsequence (LCS) algorithm to find the optimal alignment between two texts and produce the minimal diff.
Can I compare code files?
Yes. The tool works with any text including source code, configuration files, HTML, JSON, and more. The monospace font preserves code formatting.
What do the colors mean?
Green lines with a + symbol are additions (present in modified but not original). Red lines with a - symbol are deletions (present in original but not modified). White lines are unchanged.
What does "Ignore whitespace" do?
When enabled, the comparison normalizes all whitespace (spaces, tabs, multiple spaces) to a single space and trims lines before comparing. This is useful for comparing code with different indentation.
Does it run in my browser?
Yes. Once the page loads, the diff checker works entirely offline. No text data is transmitted to any server — all processing happens in your browser.
Is there a size limit?
There is no hard limit, but very large files (thousands of lines) may take a moment to process. The tool is optimized for texts up to a few thousand lines.
Guides & Tutorials
In-depth guides for every tool. Learn how to process your data privately, for free, right in your browser.
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