Plagiarism Checker (Basic)

A plagiarism checker looks for text that has been copied. This free tool is a two-text similarity checker: paste an original and a second text, and it calculates how similar they are, counts the words they share and lists matching three-word phrases. It runs in your browser, so neither text is uploaded or stored.

The similarity percentage is the share of distinct words the two texts have in common (Jaccard similarity), after lower-casing and removing punctuation. Above 70% is shown as high similarity, 41–70% as moderate and 40% or less as low. The shared phrases list shows up to 10 three-word sequences found in both texts. Those are the best evidence of copying, because shared single words are often just common vocabulary.

Limits: the tool does not search the web or any database, so it cannot tell you whether a text was copied from a source you don't have. Word overlap also ignores word order, so two texts on the same topic can score moderate similarity without any copying, and a reworded copy can score low. For web-wide checks, search for a distinctive sentence in quotes or use a web-scale service such as Copyscape.

Use it when you already have both texts: checking a writer's draft against a source article, comparing a rewrite with the original, seeing whether two pages on your site are near-duplicates, or measuring how much a quoted passage was changed. Near-duplicate pages on one site compete with each other in search, so a quick comparison helps you decide what to merge or rewrite.