Text similarity cross-check
Paste two passages to see how much wording they share. You get an overlap percentage and a list of the longest phrases the two texts have in common. This compares the two texts you provide. It does not search the web or any plagiarism database.
What this tool does
It compares the two passages you paste below and reports how much text they share. It does not search the web or any plagiarism database, and it cannot tell you whether either passage is original. Treat the score as a measure of overlap between your two texts, nothing more.
Similarity is not the same as plagiarism
This is a similarity comparison, not a plagiarism detector. It looks only at the two passages you paste in and measures how much text they have in common. It does not search the internet, journals, or any reference corpus, so it cannot tell you whether a passage was copied from somewhere else or whether it is original. A high score between two of your own drafts is expected. A high score between two unrelated sources is a cue to read both carefully yourself, not a verdict.
How the score works
The headline figure blends two measures. Shared phrasing compares ordered three-word sequences (k-grams, the basis of near-duplicate detection), so it rewards passages that repeat the same wording in the same order. Shared vocabulary compares the sets of distinct words with the Jaccard measure, which catches reuse even when sentences are reordered. The longest shared phrases list shows runs of five or more words that appear verbatim in both texts, so you can see exactly where the overlap sits.
Use it to check a quote against its source, to see how far a paraphrase has moved from the original, or to compare two of your own drafts. If you want a side-by-side diff with additions and deletions marked inline, the text comparator shows character-level changes between two versions of the same document.