ZeroClaude
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Free Claude detector

Check whether a text was written by Claude or another AI model, sentence by sentence.

0/15,000 Characters

How we detect Claude text

Our classifier is trained on human writing and on text from about 30 current AI models, including models from Anthropic. It combines two independent signals: how predictable each word is to a language model, and the style of the passage. It does not depend on spotting a few telltale phrases, so it keeps working as Claude changes.

Sentence-level highlights

See which sentences read like Claude, not just one overall score.

Low false positives

Thresholds are calibrated on human English and Chinese writing.

PDF report

Export the result as a PDF to keep or share (paid plans).

API

Check text from your own app with the JSON API.

FAQ

Your questions, answered

Can it tell Claude apart from other AI models?
No. It estimates whether a text was written by AI; it does not say which model wrote it. Text from Claude and from other current models is detected the same way.
Does it catch Claude text that was rewritten or paraphrased?
Often, yes. In our tests, AI text that another model rewrote to sound human was still caught 80% to 98% of the time, depending on the rewriting model and the language. See how detection works.
Is it free?
Yes. You can check up to 15,000 characters at a time without an account. Paid plans raise the limit and add PDF reports and batch upload.
Which languages does it work in?
Detection is trained and calibrated for English and Chinese. Text in other languages can be checked, but the result is marked as experimental until we have checked that language for false positives.
Do you keep my text?
No. Your text is only used to produce the result and is never written to a database. If you are logged in, your history keeps the score and date, not the text.
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