AI Detection
How to tell if an essay was written by AI
Start with the essay, not the percentage. A scan shows where to look. The writer, the drafts, and the sources still decide what happened.
You can check an essay for AI writing in a few minutes. The useful result is not a yes or no. It is a short list of passages worth reading again, plus the context only a person can supply.
Start with a scan
Paste the essay into the free AI detector, or upload a PDF, DOCX, or TXT file from a Certaffy account. A visitor without an account can run 3 score summaries a day, up to 2,000 words each. A free account includes 3 full highlighted reports, then 1 score-only scan a day up to 800 words.
Read the band before you read the number:
- 0–29% is a low AI signal. Continue a normal review. It is not proof the essay is human-written.
- 30–74% means review is required. Open the highlights, the draft, and the citations before any decision.
- 75% or higher is an elevated AI signal. The writing shows patterns often seen in AI text. A conversation and a look at the draft are still required.
Read the highlighted passages
A single percentage hides where the signal sits. Open the highlights and read each marked passage with the sentences around it. Ask:
- Does this paragraph sound like the rest of the essay, or like a different writer dropped in?
- Are the examples, names, and class details ones this student would know?
- Is a citation, quotation, or required template sitting inside a highlight? Those lines are easy to misread.
If the file is a PDF, confirm the extracted text matches the pages. A scan of a photo, a text box, or a two-column layout can score the wrong words. Our PDF checklist covers that check.
Ask for the work behind the essay
The scan cannot see the desk. Before you treat a high score as an answer, look for the writing process:
- Earlier drafts, outlines, or notes.
- Sources the writer can open and explain.
- A short conversation: what was the hardest paragraph, and why did they choose that example?
A student who can walk through the draft, the sources, and a revision is giving you evidence the score does not contain. A student who cannot explain a highlighted page is giving you a reason to keep reviewing. Neither result is automatic proof.
What a scan cannot do
Edited AI writing, mixed drafts, and very short answers are harder to read from a score alone. A formal or highly edited human essay can also pick up a higher signal. Use the false-positive guide when a result would affect a grade.
Certaffy reports a probabilistic signal and the passages behind it. The decision stays with the teacher.
When you want the full report, highlighted passages, and a PDF you can keep, start from Certaffy for Education or compare plans on pricing.