How does the diff algorithm work?

The tool uses a line-by-line diff algorithm (based on the Myers diff algorithm) that compares the two texts line by line. It identifies added lines (present in the new text but not in the original), removed lines (present in the original but not in the new text), and unchanged lines.

What do the colors mean?

Green background = added lines (present in the new text only). Red background = removed lines (present in the original only). Within modified lines, darker color shades indicate character-level insertions (green) or deletions (red). Neutral lines have no background.

Can I compare code files?

Yes. The diff checker works with any text-based content including source code, Markdown, HTML, JSON, and configuration files. Line-by-line comparison is ideal for code reviews and tracking revisions.

Is there a limit on text size?

The tool runs entirely in your browser, so the practical limit depends on your device's memory. For most use cases (documents up to thousands of lines), performance is smooth. Very large files (10,000+ lines) may experience slower rendering.

Is my text sent to a server?

No. All diff computation happens entirely in your browser using JavaScript. Your text is never uploaded, stored, or transmitted anywhere.

Tools

Original

Modified

Text Diff Checker — Compare Text and Find Differences

Free online text diff checker tool. Compare two texts side by side and instantly see added, removed, and changed lines. Perfect for tracking document revisions, comparing code changes, proofreading edits, and reviewing content updates. Features a clean line-by-line diff view with color-coded highlights. 100% browser-based — no data upload required.

Features

✓Side-by-side text comparison with color-coded line differences
✓Added lines shown in green, removed lines in red, unchanged lines in neutral
✓Line-by-line diff granularity for precise change tracking
✓Auto-detect changes as you type in either text panel
✓Swap button to exchange text between left and right panels
✓Clear both panels with one click
✓Sample texts to quickly see how the diff tool works
✓Character-level change highlighting within modified lines
✓Handles large texts efficiently
✓100% browser-based — your text never leaves your device

How to Use

1Paste the original text in the left panel (Original) and the modified text in the right panel (Modified).
2The diff result updates automatically — lines with changes are highlighted in color.
3Green highlights indicate added content; red highlights indicate removed content.
4Review each changed line — modified lines show character-level changes within the line.
5Click 'Swap' to exchange the two texts, or 'Clear' to start over.

Frequently Asked Questions

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