What counts as plagiarism?
Plagiarism is presenting someone else's words or ideas as your own: copying without quotation marks, paraphrasing too closely, or using a source without citing it. Citing a source never excuses a long passage copied word for word. Short quotations go in quotation marks; everything else must be in your own words, with a citation.
How to use this checker well
Run it on a draft, not on the final night, so there is time to fix what it finds. Rewrite from memory, not by swapping synonyms. For each highlighted passage decide: is it a quotation that needs marks and a citation, a common phrase, or a paragraph too close to the source? Rewrite what is too close from memory rather than swapping synonyms, then check it again.
Quotation, paraphrase or common phrase?
Not every match is a problem. A short exact quotation in quotation marks with a citation is fine, and a stock phrase will always match. What needs work is a full sentence or paragraph that follows a source closely without quotation marks, which is the pattern instructors and editors treat as copying.
Similarity is not a verdict
The score shows where text overlaps with the sources searched, not why. Names, titles and quoted passages create overlap in honest work, and a stock phrase such as "the United Nations General Assembly" will always match. Do not use the number as proof that someone cheated.
Fix and cite
If a passage matches, you have three options: quote it exactly and cite it, paraphrase it properly and cite it, or remove it. Read how to paraphrase, use the Paraphrasing Tool as a drafting aid, then build references with the Citation Generator. If your text may have been written with AI, the AI Content Detector gives a separate, clearly labelled estimate.