A
Light edits
Grammar fixes, punctuation changes and a few word substitutions may leave much of the original token sequence intact.
Claude Watermark Detector & Remover
Check text for possible Claude-style signals, understand how Claude's SynthID-style watermark works, and rewrite text naturally with an AI humanizer.
No hidden-character gimmicks · Clear methodology · Privacy-first interface
How Claude watermarking works
The watermark is in token selection — not hidden characters.
Anthropic says Claude's text watermark uses a version of Google DeepMind's SynthID-Text approach. Instead of inserting invisible Unicode characters, the system changes the source of randomness used when Claude chooses among several plausible next words.
01
ContextClaude reads the tokens that came before.02
Candidate tokensThe model has several plausible next-token choices.03
Watermark keyA secret key helps determine the pseudo-random choice pattern.04
Token choiceThe selected token still looks natural to the reader.05
Statistical signalAcross enough text, the sequence can be checked against the key.What a real detector checks
Detection requires the secret watermark key.
A normal AI detector looks for language patterns such as phrasing, token predictability or stylistic tells. Claude watermark detection is fundamentally different: it checks whether token choices are statistically consistent with Claude's watermark key.
| Method | Can verify official Claude watermark? |
|---|---|
| Invisible Unicode scanner | No |
| Em dash detector | No |
| Generic AI detector | No — only estimates AI style |
| Anthropic key / official detector | Yes |
Rewrite & humanize
Why rewriting changes the watermark signal.
Because the watermark is tied to Claude's sequence of token choices, simply deleting zero-width characters or replacing punctuation does not target the watermark. Anthropic says light editing may leave the signal partly intact, while a complete rewrite in which every word is replaced will remove the original watermark.
B
Natural rewrite
A humanizer can substantially rewrite wording, sentence structure, transitions and phrasing while preserving meaning.
C
New wording
A fully rewritten passage should be treated as newly worded content rather than the original Claude-generated sequence.
This site should not claim that a third-party score can prove whether Claude wrote a passage. Until an authorized detector is available, treat local results as heuristics and clearly label them as such.
Why this is different
No fake “hidden character” claims.
01
Science-first explanation
Explains the difference between SynthID-style statistical watermarking and ordinary invisible Unicode characters.
02
Clear detector labeling
Separates heuristic AI-style analysis from official key-based watermark verification.
03
Humanizer workflow
Moves users naturally from analysis to a full rewrite workflow without pretending punctuation cleanup removes the watermark.
FAQ
Claude watermark questions
Does Claude put invisible characters in AI-generated text?
No. Anthropic explicitly says its text watermark does not add hidden characters. The watermark is created through the random process used to choose among plausible next tokens.
Can an em dash reveal a Claude watermark?
No. Punctuation style may be a writing clue, but it is not the official watermark. Removing em dashes does not directly remove the SynthID-style statistical signal.
Can this website detect the official Claude watermark?
Not without Anthropic's authorized watermark key or official detection service. The on-page score comes from GPTHumanizer detection and is a probabilistic AI-likelihood signal. When the label is AI, this site displays CLAUDE AI. When Anthropic releases its detection API, the front end can be connected to that endpoint.
How does Claude watermark detection work?
A key-based detector checks whether the sequence of tokens is statistically consistent with the pseudo-random token-selection pattern generated from Claude's watermark key and the preceding context.
Does rewriting remove a Claude watermark?
Anthropic says light editing may not remove the watermark completely, while a complete rewrite in which every word is replaced will. Rewritten text should be treated as new wording, and no third-party tool should promise a guaranteed result without an official detector.
Does Claude watermark code?
Anthropic says watermarking is generally sparser in code because many code tokens are constrained by correctness. Comments and other places with arbitrary wording may offer more room for watermarking.
Does Claude watermark translations?
Yes. Anthropic says translations produced by Claude can carry the watermark because Claude chooses the wording throughout the translated passage.
Methodology & sources
Where these explanations come from.
Every claim on this page traces back to a public source. The checker calls the GPTHumanizer detection API and never claims Anthropic key-based watermark verification. A result labeled AI is shown as CLAUDE AI.
- Anthropic — How Claude's text watermark worksVendor documentation on watermark placement, code, translation and editing behaviour.
- Google DeepMind — SynthID TextThe token-sampling watermarking family Anthropic's approach is based on.
- Nature — Scalable watermarking for identifying large language model outputsPeer-reviewed description of the SynthID-Text method and its detectability limits.
Editorial standard: Writers and engineers who track published research and vendor documentation on text watermarking. Corrections are welcome — the page is updated when Anthropic publishes new watermarking details.
Rewrite naturally
Want a cleaner, more natural version?
Rewrite the full passage instead of deleting characters or punctuation. Connect this page to your humanizer API to create a seamless detector → rewrite workflow.
Open GPTHumanizer