Every Claude model embeds an invisible watermark mark in the text it generates, no matter where you are or how you are using an Anthropic product. The Claude Watermark Detector checks a piece of text for that signal and tells you straight, so you're not guessing whether something is clean before you publish it or trust it.
Everything you need to check, verify, and monitor Claude's watermark, whether it's one page or your whole publishing queue.
One document at a time. Paste in any piece of text, Claude's or otherwise, and get a straight read on whether the watermark is present. No account setup required to try it, and no limit on how many times you check a piece before you're confident in the result.
No vague "might be AI" language. Every check comes back with a detection score attached, so you know where a piece actually lands instead of eyeballing it and hoping.
Route content through the Watermark Detector API before it hits your CMS, your inbox, or your archive. Built for teams that need to check volume, whether that's verifying your own rewritten content stays clean or screening incoming text at scale, with turnaround fast enough to sit inside a real production pipeline.
What is Claude's text watermark, and can you detect it?
Claude's text watermark works nothing like a logo in the corner of an image. It's a pattern in the model's word choices, embedded token by token as the text is generated, invisible on the page and undetectable to the eye. Anthropic confirms it travels with the text through copy and paste, and can survive light editing. Every Claude model carries it, everywhere Claude is offered, regardless of where you or your business are based.
Anthropic has also published where the signal breaks: heavy edits, paraphrasing at the sentence level, translation, and short passages that don't carry enough of the pattern to detect. The Watermark Detector checks against that same mechanism directly, rather than relying on the surface-level guesswork older AI detectors use. A missing mark doesn't automatically mean a piece is human-written either, and the tool reports it that way instead of overstating what a clean result actually proves.
Signal checked
Accuracy on edited text
Result format
Volume
Update cadence
Still have more questions?
Learn more in our support page.
Paste the text into the Claude Watermark Detector. It checks for Claude's embedded pattern and returns a detection score, so you know whether the mark is present before you publish the piece or trust it.
Not all of it. Every Claude model embeds an invisible watermark in the text it generates. Gemini marks output through SynthID. ChatGPT has tested the approach but hasn't shipped one as of now, and most smaller or open-source models don't mark their output yet.
Yes. This tool is built around Claude's marking method. A clean result means Claude's mark wasn't found, not that no other model was involved.
No. A missing mark doesn't automatically mean a piece is human-written. Short passages, heavy edits, paraphrasing, and translation can all break or hide the signal. The detector reports a clean result as the mark not being found, not as proof of human authorship.
Yes. That's one of the main uses. Run a draft through the detector before it hits your CMS or publish button so you know whether Claude's mark is still in the text.
A general AI detector guesses from style and phrasing. The Watermark Detector checks for Claude's actual embedded pattern and returns a score, rather than a vague "might be AI" label.
Yes. The Claude Watermark Detector checks text for Claude's invisible mark and returns a detection score on every check.
You can't prompt Claude to leave the mark out. The watermark is embedded at the model level as the text is generated. To strip it, you need a structural rewrite. StealthGPT's Claude Watermark Remover is built for that.
One person checking one document, a team verifying content before it goes out, or screening submissions at scale, the check works the same way. Enterprise options are available for teams that need it running quietly in the background
