xAI adds invisible text watermarking to Grok API models

Starting November 7, 2026, Grok API output will carry a hidden statistical fingerprint by default, leaving ChatGPT as the North American holdout xAI is adding text watermarking to Grok. The company once argued that AI output should stay untouched, so this is a notable reversal. The change matters because of who is left. According to the announcement shared on X, the move leaves ChatGPT as the only model in North America that does not watermark its text. How the Grok watermark works Starting November 7, 2026, xAI will switch on invisible statistical watermarking across its Grok API models by default. Developers will not need to flip a setting. It simply arrives. The feature covers a list of model versions: grok-4.7, grok-4.6, grok-4.5, grok-4.3, and grok-4.20. If you are building on any of them, your output will carry the mark. The coverage extends to every text generation endpoint. That includes the main api.x.ai endpoint, the Responses API, and the Chat Completions API. Grok’s watermark works by nudging token selection toward a pattern. When the model chooses its next word, or “token,” the system gently nudges those choices toward a pattern. Read any single sentence and nothing lo...