Tools AI Minute Newsroom 2026-08-16

Anthropic has published where its invisible mark stops working: rewrite every word and it is gone

Anthropic put out a technical account of the watermark it started embedding in Claude's text this month, and it is unusually direct about the limits. Light editing probably will not remove the mark, the company says, but 'a complete rewrite where every word is replaced will'. Detection works poorly on short passages, because fewer word choices mean less signal to read. The mark is sparser in factual writing and in code, where there are fewer ways to say the same thing without making it wrong. And if you hand Claude a document and ask only for grammar and punctuation fixes, the watermark can live only in those few corrections, which may be too few to register. Anthropic also spells out what a positive detection means: that Claude was probably involved in producing the text — not that no human wrote it.

Why it mattersFour days ago the most-starred new AI project on GitHub was a tool for stripping exactly these marks, and Google spent the week arguing that invisible marking is the real safeguard against synthetic content. Anthropic has now conceded, in its own words, most of what the critics were saying: the mark survives copy-paste but not a rewrite, and it is weakest precisely on the short factual text that spam, fake reviews and fabricated citations are made of. If schools, publishers and courts are going to lean on watermark detectors, this is the document that tells them what a detector can and cannot prove.

✓ Verified · 2 sources

Read in the app — free, in 9 languages

Anthropic has published where its invisible mark stops working: rewrite every word and it is gone

Related stories