How the demo watermark works
This is a small, public watermark built for the demo. It is based on published green-list research.
It is not Claude’s watermark. Anthropic has not published the method it uses.
The scanner and the score
The scanner reads the original text as-is. Any character it does not recognise ends a token. That is why an invisible character inside a word can split one token into two.
The scanner combines each token with the one before it and hashes the pair with the public seed. Every distinct pair counts towards the total; the hash decides which side of the split it falls on. The marked text prefers words that land on one side.
Repeated pairs count once, so repeated text cannot inflate the score. The score shows how far the marked count is above chance. The detector then compares that score with its threshold.
- Expected marked share
- 1 in 4 token pairs
- Threshold
- 1.80
- Minimum text
- 120 distinct token pairs
Technical values
- Pattern
[A-Za-z]+(?:'[A-Za-z]+)?- Profile
- declawd-v1
- Seed
- 3af0a69fbe7c97fb6c73d2c96d7824d26782d36b6e5b6379eb0886382ce39164
- Registration
- 82dfb1128450d73970e812637a7be307901d7cdd66b53660c6eef83cb8e63d97
How the threshold was chosen
We chose the 1.80 threshold on 96 calibration passages. We then measured it on 96 passages by different authors.
The calibration target was no more than 2% above threshold. The evaluation result was 2.08%, or 2 of 96 passages. We did not change the threshold afterwards.
This is a small sample. The 95% interval is 0.57% to 7.28%, and passages by the same author may not be independent.
What this demo cannot do
- The scanner reads ASCII letters only.
- The demonstration uses fixed samples. The checker accepts text you paste, scores it in your browser and sends it nowhere. Neither accepts files.
- The repair handles only the two known character changes in the demo.
- The scores and results apply only to this demo.
Use it in a session
Use this as a five-minute prompt. Then apply the four questions to a real piece of work.
Ask what evidence exists and what would be worth keeping next time.