Per-model status
Is Claude Opus 5.5 watermarked?
Yes. Claude Opus 5.5 launched on September 22, 2026, and Anthropic's launch announcement says: "As with Fable 5.1, Opus 5.5 comes with our watermarking measures to comply with the EU AI Act." Anthropic's support page lists its text watermark in Claude, Claude Code, Claude Cowork and the Claude API and through AWS, Google Cloud and Microsoft Foundry.
Anthropic describes the watermark as imperceptible and part of the text itself, so it travels with copy and paste and may persist through some editing. Files Opus 5.5 creates also carry Content Credentials (C2PA). There is no public way to check a piece of text for the watermark (see the FAQ below).
Where Anthropic marks Opus 5.5 output
- Text watermark in Claude, Claude Code, Claude Cowork and the Claude APIYes
- Text watermark through AWS, Google Cloud and Microsoft FoundryYes
- Content Credentials (C2PA) on files it createsYes
From the model table on Anthropic's support page, checked November 12, 2026.
FAQ
Is Claude Opus 5.5 watermarked?
Yes. Anthropic's support page lists Claude Opus 5.5 as carrying its text watermark in Claude, Claude Code, Claude Cowork and the Claude API and through AWS, Google Cloud and Microsoft Foundry. It launched after the August 2, 2026 cutoff, and Anthropic says models launched on or after that date are marked from launch.
Can anyone detect Claude Opus 5.5 output?
Not publicly. Anthropic's watermark detection is in private preview. It is available to eligible organizations such as regulators, law enforcement, media, fact-checkers, independent researchers, educational organizations and EU civil society groups, and to enterprises that need to check their own Claude output. Anthropic says it plans to expand access over time. Its free Content Checker checks files for Content Credentials, not text.
Does the Opus 5.5 watermark survive editing?
Partly, according to Anthropic. It says the watermark travels with text that is copied and pasted and may persist through some editing, but that text which has been heavily edited, paraphrased or translated, or a very short passage, may carry no detectable mark. There is no public detector, so you cannot test a piece of text yourself.
How do I remove the watermark from Claude Opus 5.5 output?
A complete rewrite through a different, non-watermarking model changes the word choices the watermark lives in. ClaudeRewrite does this automatically using DeepSeek V4 Flash and is designed to keep your facts, numbers and meaning intact. Because there is no public detector, the result cannot be independently verified.
Sources
Related guide: Does Claude Opus 5.5 watermark its text?