Free Plagiarism-Style Similarity Checker — Compare Two Texts
Whether you are a teacher spotting copied essays, a blogger verifying freelancers, or a student checking your paraphrase went far enough, comparing two documents side by side is tedious. This free checker quantifies overlap between any two pasted texts with a similarity percentage, shared-keyword highlights, and component scores — computed locally with set-based text algorithms.
How to Check Similarity
- Paste both texts — original on the left, suspect copy on the right. Works with essays, articles, code comments, and product descriptions.
- Click Compare Texts — the tool tokenizes both documents and runs two independent measures instantly.
- Read the score — above 80% means near-duplication, 50–80% significant shared passages, 25–50% common phrasing, below 25% essentially original.
- Review shared keywords — highlighted terms show exactly which vocabulary overlaps, so you can judge intent, not just numbers.
How the Score Works: Jaccard + Bigrams
The final percentage blends two classic measures. Jaccard similarity divides shared unique words by total unique words — a pure vocabulary-overlap gauge immune to document length. Bigram Dice similarity compares adjacent word pairs, catching copied phrasing even when a few words changed. Weighting sequence matching at 60% makes reworded-but-copied passages score higher than coincidental shared vocabulary, which mirrors how human reviewers actually judge duplication.
Is this a substitute for Turnitin?
No — this compares two texts you provide; it cannot search the web or academic databases. For originality-against-the-internet checks, pair it with a search-engine spot check of suspicious sentences in quotes.
Why did paraphrased text still score high?
Swapping synonyms keeps most bigrams intact ("fast car" → "quick car" shares nothing, but longer shared runs survive). Genuine rewriting changes sentence structure, which drops the sequence score fast.
Is my text uploaded anywhere?
No. Tokenization and scoring run in page JavaScript; pasted essays and drafts never leave your browser.
Related Tools
Measure output volume with the Word Counter, normalize casing before comparing with the Case Converter, and find exact line differences with the Diff Checker.