Text Compare / Diff
Compare two texts side-by-side and see differences highlighted. Line-by-line diff with character-level change detection. Perfect for code reviews, document edits, and version comparison.
Compare Text in 3 Steps
Paste your original and modified texts, click Compare, and see every difference highlighted instantly. Character-level precision shows exactly what changed.
Text Compare / Diff - Line-by-Line Difference Checker
This Text Compare tool finds every difference between two texts using a Longest Common Subsequence (LCS) based diff algorithm - the same approach used by Git and professional diff tools. Paste your original and modified texts, click Compare, and see additions, deletions, and changes highlighted with color-coded precision.
Unlike basic text comparison tools that only flag whole-line differences, this tool also performs character-level highlighting within changed lines - showing you exactly which words or characters were modified, not just which lines differ.
Key Features
git diff output. Compact view for reviewing changes sequentially.This Tool vs. Other Diff Checkers
| Feature | Basic Diff Tools | This Tool |
|---|---|---|
| Character-level diff | Rarely | ✓ Within changed lines |
| Side-by-side + unified | Usually one | ✓ Both views |
| Diff navigation | Sometimes | ✓ Prev/Next buttons |
| Ignore case option | Sometimes | ✓ Plus whitespace & trim |
| Similarity % | Rarely | ✓ Calculated automatically |
| Copy diff output | Sometimes | ✓ One-click copy |
| Privacy | Varies (server-side) | ✓ 100% browser-based |
| Character limit | Varies | 100,000 per side |
How the Diff Algorithm Works
The tool uses a three-stage process to find differences accurately.
First, it splits both texts into lines and computes the Longest Common Subsequence (LCS) - the largest set of lines that appear in both texts in the same order. Lines not in the LCS are flagged as added or removed.
Second, adjacent remove-then-add pairs are detected and reclassified as "changed" lines - meaning the line was modified rather than deleted and replaced.
Third, for each changed line pair, a character-level LCS highlights exactly which characters were altered. For performance, lines over 500 characters skip character-level analysis and highlight the entire line.
Common Use Cases
FAQs – Text Compare / Diff
This tool uses a Longest Common Subsequence (LCS) based algorithm for line-level comparison, similar to what Git uses. For changed lines, it runs a second character-level LCS to highlight exactly which characters differ.
Side-by-side shows original and modified texts in two synchronized columns. Unified view shows everything in a single column with - and + prefixes, similar to git diff output. Both views include character-level highlighting.
Green (with + prefix) indicates added lines. Red (with - prefix) shows removed lines. Amber shows changed lines - lines that were modified rather than fully added or removed. Within changed lines, red strikethrough marks deleted characters and green highlights added characters.
When enabled, the comparison treats uppercase and lowercase letters as identical. "Hello" and "hello" would be considered the same line. The display still shows original case.
When enabled, multiple spaces, tabs, and other whitespace characters are treated as a single space during comparison. This is useful for code where indentation may vary but content is identical.
Each text area supports up to 100,000 characters. For texts with more than 5,000 lines, the tool shows a warning as processing may take longer. Character-level diff is skipped for individual lines longer than 500 characters for performance.
Similarity is calculated as (unchanged lines ÷ maximum of original or modified line count) × 100. A similarity of 100% means both texts are identical. 0% means no lines in common.
Yes. The diff output uses a monospace font and preserves whitespace, making it suitable for comparing code, configuration files, JSON, YAML, and any structured text. Use "Ignore whitespace" if indentation differences aren't important.
No. All comparison processing happens entirely in your browser using JavaScript. Your text never leaves your device. No data is stored, logged, or transmitted.
It copies the entire diff output as plain text with - and + prefixes for changed lines and spaces for unchanged lines. You can paste it into code reviews, emails, or documentation.
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Line-by-line diff with character-level highlighting. Side-by-side and unified views. Free, private, browser-based.
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