Which Claude models are watermarked?
Anthropic marks text from Claude models launched on or after 2 August 2026. Here is where each shipped model falls.
Last checked 2026-09-02.
| Model | Launched | Watermarked |
|---|---|---|
| Claude Fable 5.1 | 1 September 2026 | Yes |
| Claude Mythos 5.1 | 1 September 2026 | Yes |
| Claude Opus 5 | 24 July 2026 | No |
| Claude Sonnet 5 | 30 June 2026 | No |
| Claude Fable 5 | 9 June 2026 | No |
| Claude Mythos 5 | 9 June 2026 | No |
| Claude Opus 4.8 | 2026, before 2 August | No |
| Claude Haiku 4.5 | 1 October 2025 | No |
Public tools cannot check the mark directly. Anthropic’s detector is in private preview for eligible organisations. What anyone can verify today is the HTML and Unicode Claude’s interface leaves on the clipboard — paste your text in and see.
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