Free Text Comparator Online
Compare two documents side by side and find similarities and differences. Great for plagiarism checking. 100% client-side — your text stays private.
How to Use the Text Comparator
- Paste or type text into both "Text A" and "Text B" panels.
- Click "Compare" to analyze similarity.
- View the similarity percentage using Jaccard index and cosine similarity.
- Toggle between word-level and character-level comparison.
- Review the frequency analysis for the most common words in each text.
- Check the n-gram overlap for deeper structural comparison.
Why Use This Text Comparator
Whether you're checking for plagiarism, comparing document revisions, or verifying originality, this tool gives you a clear picture of how two texts relate. The side-by-side view makes visual comparison easy.
Unlike simple diff tools, this comparator calculates Jaccard index and cosine similarity, provides word frequency analysis, and supports both word-level and character-level comparisons — all while keeping your data 100% private.
How It Works
The Text Comparator uses two complementary algorithms to measure text similarity. Jaccard similarity treats each text as a set of unique words (or characters) and calculates the ratio of shared items to total items. A Jaccard score of 0.8 means 80% of the unique words appear in both texts.
Cosine similarity builds frequency vectors for each text and calculates the cosine of the angle between them. This is less sensitive to text length differences — a short summary and its full article will score higher with cosine than with Jaccard. The tool also performs n-gram analysis, comparing sequences of 2 or 3 words to detect shared phrases and sentence structures beyond single-word matching.
Similarity Metrics Reference
| Metric | Formula | Range | Best For |
|---|---|---|---|
| Jaccard Index | |A ∩ B| / |A ∪ B| | 0.0 – 1.0 | Detecting unique vocabulary overlap; penalizes length differences |
| Cosine Similarity | (A · B) / (||A|| × ||B||) | 0.0 – 1.0 | Comparing texts of different lengths; measuring topical similarity |
| Shared Words | Count of common words | 0 – max(|A|, |B|) | Raw volume of shared content |
| N-gram Overlap | Shared n-grams / total unique n-grams | 0.0 – 1.0 | Detecting copied phrases, sentence structure similarity |
Examples
| Comparison | Jaccard | Cosine | Interpretation |
|---|---|---|---|
| Same text vs. itself | 100% | 100% | Identical content — expected result |
| Original vs. paraphrase | 30–50% | 60–80% | Same meaning, different words — cosine catches the similarity |
| Original vs. heavily edited version | 50–70% | 80–95% | Minor changes — high similarity on both metrics |
| Two articles on different topics | 5–15% | 10–30% | Low overlap — some shared stop words inflate scores |
| Short excerpt vs. full document | 20–40% | 50–70% | Cosine handles length mismatch better than Jaccard |
Frequently Asked Questions
Jaccard similarity measures the size of the intersection divided by the size of the union of two sets. A score of 1.0 means identical content, while 0.0 means no overlap.
Cosine similarity measures the cosine of the angle between two vectors (word frequency vectors in this case). It ranges from 0 (no similarity) to 1 (identical direction). It's less sensitive to text length differences.
No. All comparison happens entirely in your browser. Your text is never transmitted anywhere, making this tool safe for confidential or sensitive documents.
N-grams are contiguous sequences of n words. Bigrams (2-grams) or trigrams (3-grams) help detect shared phrases and sentence structures, going beyond single-word matching.
Use Cases
Document Version Comparison
Comparing two versions of a document side by side reveals exactly what changed between drafts and revisions.
Config File Differences
Finding differences between configuration files helps identify what changed when debugging deployment issues.
Contract Amendment Checks
Checking contract amendments ensures no unauthorized changes were made to legal documents between versions.
Text Change Verification
Verifying text changes before publishing ensures accuracy and catches unintended modifications in content.
Side-by-Side Text Analysis
Side-by-side text analysis provides a clear visual comparison of similarities and differences between two passages.