How to remove a SynthID watermark
SynthID-Text is Google DeepMind’s watermark for AI-generated text — and in 2026 it went mainstream when Anthropic announced Claude would adopt a SynthID-style approach. Here’s what it is, why it’s hard to remove by editing, and how to strip it properly. You can do it free with Unmark.
What SynthID actually does
When a language model writes, it repeatedly samples the next word from a probability distribution. SynthID nudges that sampling with a secret pseudo-random key so the chosen words follow a subtle statistical pattern across the whole passage. Nothing is visibly different — the text reads normally — but a detector holding the key can measure the pattern and estimate whether the text was machine-generated. Because the mark lives in the sequence of word choices, it doesn’t rely on hidden characters or metadata.
Why editing a few words doesn’t remove it
The watermark is distributed, not localized. Swapping a word here and there, fixing punctuation, or trimming a sentence leaves most of the pattern intact — often enough for a detector to still flag it. The only reliable way to remove a statistical watermark is to change enough of the token sequence that the pattern no longer holds, i.e. a genuine rewrite.
How to remove it
- Paste the text into Unmark.
- Choose a rewrite strength and remove the watermark. Unmark rewrites the wording to disrupt the statistical pattern while preserving your meaning, and strips any invisible characters in the same pass.
- Copy the clean text and re-read it to confirm the meaning is intact.
A realistic expectation
Rewriting substantially degrades SynthID and other detector signals, and heavier rewrites degrade them more — but no tool can guarantee text is permanently undetectable against every detector. Treat watermark removal as best-effort, and always review the result.
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