Free watermark check
No account, no word limit, no email address. It costs nothing to run, so it costs you nothing.
Paste, do not retype — invisible characters only survive a copy.
Click to choose a file
No account, no word limit
We never ask for a name, an email address or a university.
No invented number
Separate findings, not one percentage. Style is never counted as evidence.
Says what it cannot do
Claude's statistical watermark is checkable by nobody today, including us.
This watermark checker is free with no sign-up, no email address and no word limit, and it will stay that way. The detection is character arithmetic that runs in your browser, so there is no expensive model to pay for and nothing to meter. It finds invisible Unicode characters, hidden encoded messages and mixed-alphabet words, and it tells you plainly that Claude's actual statistical watermark cannot be checked by any public tool today.
Copy rather than retype — invisible characters only survive a copy-paste. PDF, DOCX and TXT are read locally, and a DOCX also gives up its editing time and save count.
You are never asked for a name, an email address or a university. The text is analysed in your browser and the analysed text is then stored on our EU servers for twelve months, never linked to your identity.
You get one card per layer, each with its own confidence, and no combined percentage. Character findings are definite. Style habits are not evidence and are labelled as such.
Because it costs us almost nothing. Every layer of this check is arithmetic over the characters in your text, and your browser does it in milliseconds. There is no API call and no model inference, so there is no marginal cost to pass on and no reason to put a limit on it.
That is also why there is no paid tier here and no upsell inside the result. Where we do charge — the full AI check, at €4.99 once — it is for something that genuinely costs money to run.
The honest one: this check answers a narrower question than you probably want answered. It tells you what invisible characters are in your document. It cannot tell you whether Claude wrote your text, because nobody can do that yet, and it cannot tell you whether a university's AI detector will flag you.
If that second question is the real one, our AI check is the tool for it, and it publishes its false-positive rate beside every verdict — free for the first 1,500 words.
That is what universities actually run, and those detectors are wrong about human writing more often than they admit. Our AI check publishes its false-positive rate beside every verdict. Free for the first 1,500 words.
Run the free AI check