Plagiarism Checker (Text Compare)

The Plagiarism Checker compares two pieces of text against each other and reports how similar they are — an overall similarity score based on shared 5-word phrases, plus a list of sentence pairs that are near-duplicates between the two documents. It's a private way to compare documents against each other, not a web-search-based plagiarism scanner.

It's used to check a rewrite against its original source before publishing, compare two student submissions for a duplicate content checker pass, verify that spun or paraphrased marketing copy is genuinely different from the reference it was based on, and check your own draft doesn't track a cited source too closely even when you believe you've paraphrased it well enough. Editors also use it to compare two versions of an article at different stages of an edit to see how much text actually changed versus how much just looks different.

The overall score comes from 5-word phrase (shingle) overlap between the two texts — a text similarity method that catches near-verbatim copying and light paraphrasing far more reliably than comparing whole sentences or whole documents, since even a heavily reworded paragraph tends to leave a few unchanged 5-word runs behind. On top of the headline number, sentence-level matching lists each near-duplicate pair with its own overlap percentage, so you can jump straight to the specific lines worth reviewing rather than re-reading both documents end to end. It handles documents thousands of words long instantly.

Unlike web-based plagiarism services, this tool doesn't search the internet or any external index — it's a private, local comparison between exactly the two texts you paste, and nothing is uploaded, indexed or retained. There's no universal threshold for what counts as plagiarism: above roughly 30% phrase overlap between two independently written documents is unusual, and above 60% almost always indicates direct copying or only light paraphrasing, but always read the flagged sentence pairs yourself — short, common phrases and standard idioms can inflate the score on otherwise unrelated short texts.