How LLM Text Watermarking Works: A Technical Breakdown

arpit_bhayani · x · 2026-08-15

Arpit Bhayani explains the mechanism behind Anthropic's text watermarking. When an LLM generates a token, it often chooses from candidates with nearly tied probabilities. The watermarking technique replaces the standard random seed with a value derived from a secret key plus the previous tokens. To the user, the output still appears random. However, anyone with the key can verify if the sequence of choices matches the derivation rules, providing a probabilistic indicator that the text was written by Claude.

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