Compare two texts to detect similarity. Sentence-by-sentence analysis using Jaccard similarity.
This Plagiarism Checker compares two blocks of text side by side and reports how similar they are, highlighting the phrases and sentences they share. Paste an original passage into one field and the text you want to check into the other, and the tool measures overlap at the word and phrase level, then returns a similarity percentage along with the matching segments. It works entirely in your browser on plain text you provide, so there are no accounts, uploads, or file limits.
Students use it to compare a draft against a source before citing, teachers use it to spot copied passages between two submissions, and writers and editors use it to confirm that a paraphrase is genuinely reworded rather than a lightly edited copy. Because it compares the two texts you supply rather than crawling the web, it is fast, private, and useful for direct one-to-one checks.
The tool normalizes both texts first, lowercasing them and stripping extra punctuation and whitespace so that differences in formatting do not count as differences in content. It then breaks each text into overlapping word sequences called n-grams (for example, 3-word shingles) and compares the sets of shingles from both texts.
Similarity is typically reported using a set-overlap measure such as the Jaccard index, which divides the number of shared shingles by the total number of unique shingles across both texts: J = |A intersection B| / |A union B|. A score near 100 percent means the passages are nearly identical, while a low score means little verbatim overlap. Matching phrases are then highlighted so you can see exactly which sequences the two texts share.
Because it measures literal word overlap, the checker is best at catching copy-paste and lightly edited text. A thorough paraphrase that keeps the meaning but changes the wording and sentence structure will produce a low similarity score, which is expected. This is a comparison tool between two texts you provide, not a search against published sources or the internet.
Yes, it is completely free with no sign-up. The comparison runs in your browser on the two texts you paste, so your content is not uploaded to a server or stored, making it safe for unpublished drafts and coursework.
No. This tool compares only the two texts you enter against each other. It does not search Google, journals, or any external database, so it is designed for direct A-versus-B comparisons rather than web-wide originality checks.
It is the proportion of shared word sequences relative to the combined content of both texts. A high percentage indicates substantial verbatim overlap, while a low percentage means the passages use mostly different wording.
Usually not, if it is genuinely reworded. The tool measures literal word and phrase overlap, so changing vocabulary and sentence structure lowers the score. A high score on a paraphrase suggests it is still too close to the original.
There is no universal cutoff, since short quoted material or common phrases naturally match. As a rough guide, matches on long, distinctive sentences are more concerning than scattered short phrases, and any exact copying should be quoted and cited.
There is no fixed word limit, but very large passages take longer to compare in the browser. For best speed and clarity, compare one section, chapter, or essay at a time.
Yes. Paste one submission into each field and the tool will highlight shared phrasing and report the overlap, which helps identify passages that may have been copied between the two documents.