Per-model status
Is Claude Sonnet 5.5 watermarked?
Yes. Anthropic's support page lists Claude Sonnet 5.5 as carrying the text watermark in Claude, Claude Code, Claude Cowork and the Claude API and through AWS, Google Cloud and Microsoft Foundry. Sonnet 5.5 launched on September 28, 2026, after the August 2, 2026 cutoff, and Anthropic says models launched on or after that date are marked from launch.
Anthropic's Sonnet 5.5 launch announcement does not mention watermarking, so the model table on its support page is the place that settles it. Files Sonnet 5.5 creates also carry Content Credentials (C2PA).
Updated November 12, 2026. This page previously listed Sonnet 5.5 as not confirmed, because its launch announcement does not mention watermarking.
Where Anthropic marks Sonnet 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 Sonnet 5.5 watermarked?
Yes. Anthropic's support page lists Claude Sonnet 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 Sonnet 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 Sonnet 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 Sonnet 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: How to remove the watermark from Claude Sonnet 5.5 output