# How the plagiarism check works

> What we compare your text against, what a check costs, and how to keep quotes and references out of the score.

Canonical page: https://winstonai.ai/help/how-plagiarism-check-works

Help center: Plagiarism. Updated 2026-09-25.

A plagiarism check looks for passages that match existing sources. It answers a different question from AI detection: AI-written text is usually new, so it rarely matches anything. Running both together gives you the full picture.

## What we compare against

- Public web pages, found by searching for the most distinctive sentences in your text, plus pages fetched for earlier checks.
- Your library: every document already in your workspace. Documents are never compared with other customers' files.
- PDFs, paywalled journals and books aren't included.

## What it costs

A plagiarism check uses 2 credits per word, on top of 1 credit per word for AI detection. A 1,000-word essay checked for both uses 3,000 credits. You'll see the total before the scan starts.

## Keeping quotes and references out

Quoted passages and reference lists match their sources by design, so text in quotation marks and a reference list at the end of the document are left out of matching automatically. The report shows how many words were left out.

> **Tip:** Plagiarism checks are included on the Advanced and Team plans.