What this check tells you
This Claude watermark detector inspects only the text you paste. It reports matches from the checker’s defined set of invisible Unicode characters, special spaces, and literal HTML metadata tags. It does not infer who wrote the text or which application produced it.
This Claude watermark checker is diagnostic: it leaves the pasted text unchanged. If you decide the reported items are unwanted, use the CleanText removal tool and compare the cleaned result with the original.
Why the three result groups are separate
- Hidden characters counts each matched invisible Unicode character. Unicode documents that some layout controls are not visibly rendered even though they can affect line breaking, word breaking, glyph selection, or text direction.
- Special spaces counts the two space characters this checker handles separately: no-break space and narrow no-break space. They remain space characters, so the removal tool normalizes them to ordinary spaces instead of deleting them.
- Metadata tags counts literal
<meta ...>markup found in pasted HTML. A tag is counted once as markup, not as a group of hidden characters. The HTML Standard defines themetaelement as document metadata.
Sources: Unicode Standard, Chapter 23 and the HTML Standard’s meta-element section.
How to read each number
- A positive number means the pasted input contains that many matches in the named category.
- A zero means the checker found no match from its covered set in that category for this input.
- Neither result identifies a source. A match cannot establish an author, an AI model, an application, or an intention to watermark the text.
What this checker cannot detect
Anthropic describes its Claude text-watermarking method as a pattern in word choices and says that nothing is added to the text and there are no hidden characters. A character scan therefore cannot detect that statistical signal. Read the distinction on the Claude watermark explanation page or in Anthropic’s official explanation.
What stays local and what does not
The check on this page runs in your browser and does not upload the pasted text. The standard “Remove hidden characters” action on the main cleaner also runs locally. The optional “AI rewrite” action on the main cleaner is different: selecting it sends the text to the site’s server-side Cloudflare Workers AI service.
Questions about the checker
Does a positive hidden-character count prove that Claude wrote the text?
No. It proves only that the supplied input contains characters matched by this checker. It cannot determine authorship or origin.
What does a zero in all three categories mean?
It means this checker found none of its covered hidden characters, special spaces, or literal HTML metadata tags in that input. It is not a general proof that the text has no watermark of any kind.
Why are metadata tags not included in the hidden-character total?
They are HTML markup rather than individual invisible Unicode characters, so the checker reports them as a separate tag count.
Does the checker upload my pasted text?
No. Checking is performed locally in the browser. The separate AI rewrite action available on the main cleaner is the action that sends text to server-side AI.
Can this page detect Anthropic’s statistical text watermark?
No. Anthropic says its method uses word-choice patterns and does not add hidden characters, so this character-and-markup checker is not a detector for that signal.