Disclaimer
This is a teaching demonstration. It is not a detector, and its results are not evidence. Last reviewed 12 August 2026.
Do not use anything on this site to judge a person.
Do not use its scores, reports or figures for decisions about authorship, employment, assessment, academic conduct, discipline, or any legal or forensic matter.
The demo shows two limits. A small edit can change the score, and human writing can cross the threshold. 2 human passages cross this site’s own threshold. Treating this score as proof would be a mistake.
What the watermark here is
It is a small public scheme inspired by published research. It marks and scores only the fixed samples on this site.
It does not detect, reproduce, remove or work with the watermark used by Claude or any other product. Anthropic has not published its method.
The fixed-sample limit is a guardrail against casual misuse, not a security boundary. The method and seed are public.
Affiliation and trademarks
This site is independent. It is not affiliated with, sponsored by or endorsed by Anthropic or any other company named here. Claude and Anthropic are trademarks of Anthropic. Other names are the trademarks of their owners.
Accuracy and limits
Every figure describes one small scheme, one fixed sample and two corpora containing 192 passages. None is a general result about watermarking, a product, or AI-assisted writing.
The research on the sources page is cited so that you can read it yourself. The site is provided as it is, without warranty of any kind.
Source material
The human passages come from public-domain works listed on the sources page.
The typefaces are Newsreader and Public Sans under the SIL Open Font License. Their licences ship with the site: Newsreader and Public Sans.