How to Read Your Plagiarism and AI Scores

Updated September 26, 2026

Short answer

Your plagiarism score is the share of your text that matches other sources — not a measure of wrongdoing. Your AI score is the detector’s overall estimate of AI-generated writing, backed by the individual sentences it flags. Look at the sources and flagged passages behind each number before deciding anything.

The plagiarism (similarity) score

The plagiarism percentage shows how much of the checked text matches text found in other sources. Each source is listed with its matches, and in the Google Docs™ add-on, with the share of your document it covers. The verdict label follows the score:

0% — no matches found.
1–9% — low similarity.
10–24% — some similarity.
25–49% — significant similarity.
50% and above — high similarity.

A match isn’t automatically a problem. Quotations you’ve cited, your reference list, common phrases, names and technical terms all match other text. That’s why the sources matter more than the number: open each one and ask whether the passage is quoted and cited, a paraphrase that’s too close, or just ordinary wording. In Google Docs you can leave out quotes and references so they don’t count.

There’s no universal “acceptable” percentage. It depends on the assignment, the subject and your institution’s policy — a well-cited literature review can legitimately score higher than an opinion essay.

The AI score

The AI score is the detector’s overall estimate of AI-generated writing in the text. Below it you’ll see the sentences it flagged, each with its own likelihood. Sentences the detector rates under 40% aren’t listed, and very short sentences aren’t scored on their own.

Under 20% — mostly reads as human-written.
20–49% — mixed signals; some passages may look AI-like.
50% and above — likely AI-generated or AI-assisted. The Chrome™ extension splits this into “Likely AI-assisted” (50–79%) and “Likely AI-generated” (80% and above).

In the Google Docs add-on, flagged passages are grouped and tagged Highly likely (90% and above), Likely (60–89%) or Possible (40–59%).

Reading both together

High plagiarism, low AI: text copied or closely paraphrased from human-written sources. Check citations.
Low plagiarism, high AI: original wording that reads like machine-generated text. Look at the flagged passages; they may simply be formal or formulaic.
Both high: text that matches existing sources and reads as AI-written — worth a careful review.

Honest limits

No plagiarism or AI detector is perfect. Plagiarism checkers can’t see every book, paywalled article or private document, and AI detectors can flag human writing and miss edited AI text. Scores also differ between tools. Treat any result as evidence to review — never as proof on its own.

Where to see more detail

Open full report (in the extension and the add-on) opens the complete report on the website, with every match and sentence. Checks you run while signed in are saved to your history. See also How to check for plagiarism in Google Docs and Check any text box or highlighted text.