Text Diff Checker — Free Online Text Comparison Tool
Free online text diff tool. Compare two texts side by side, find differences with color-coded highlights. Supports code, docs, any text. Browser-based.
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.
- 6Use sample texts to understand the diff output format before comparing your own documents.
- 7Copy the diff result to share with your team for collaborative review.
- 8Compare configuration files side by side to spot deployment changes between versions.
Frequently Asked Questions
How does the diff algorithm work?
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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?
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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?
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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?
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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?
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No. All diff computation happens entirely in your browser using JavaScript. Your text is never uploaded, stored, or transmitted anywhere.
What is the Myers diff algorithm?
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The Myers diff algorithm, developed by Eugene Myers in 1986, is an efficient algorithm for finding the longest common subsequence (LCS) between two sequences. It's the foundation of the Unix diff tool and Git's merge system. It produces minimal, human-readable diffs by finding the shortest edit script that transforms one text into another.
Can I use this tool for competitive programming or coding interviews?
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Yes. Many coding problems involve character-by-character comparison. You can use this diff tool to compare your output against expected output, spot differences in algorithm implementations, or review code changes during pair programming sessions.
How does character-level diff work within a modified line?
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When two lines differ but have shared content, the tool runs a second diff on the line itself. Characters that were removed are shown with a darker red background; characters that were added show with a darker green background. This makes it easy to see exactly what changed within a line.
What are common use cases for text diff checking?
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Common uses include: code reviews (comparing commits or branches), document version tracking (comparing drafts), plagiarism detection (comparing student submissions), configuration management (comparing config files), content editing (tracking changes), and data validation (comparing CSV/JSON exports).
How is this different from Git diff?
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Git diff compares tracked files within a repository and shows changes per commit. This tool compares any two arbitrary texts without requiring version control. It's more flexible for one-off comparisons but doesn't have branching, staging, or commit history features.
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