Per-model status
Is Claude Sonnet 5 watermarked?
No, Claude Sonnet 5 does not watermark its text output as of August 2026, because it launched before Anthropic's August 2, 2026 watermarking cutoff. Anthropic has said it will retrofit watermarking to older models, so this is expected to change.
Sonnet 5 shipped before the watermarking cutoff, so its text output is not statistically watermarked today. As with the other current models, a retrofit would mark output generated after the retrofit date, not text generated before it.
FAQ
Is Claude Sonnet 5 watermarked?
Not as of August 2026. Claude Sonnet 5 launched before the August 2, 2026 cutoff, so its text output carries no statistical watermark today.
Can anyone detect Claude Sonnet 5 output?
No. Anthropic announced a detection API but has not shipped it, and no third-party tool can read the statistical watermark. Even once it ships, only output from a marked model would be detectable.
Will Claude Sonnet 5 get watermarked later?
Anthropic has said it is working to add watermarking to models released before the cutoff. If that happens, output generated after the retrofit would be marked, while text you generated before it would not be.
How do I remove the watermark if Claude Sonnet 5 gets retrofitted?
A complete rewrite through a different, non-watermarking model breaks the statistical pattern. ClaudeRewrite does this automatically using DeepSeek V4 Flash, preserving your facts, numbers, and meaning.