What is Google-Extended?

Google-Extended is a robots.txt token that lets a site opt out of having its content used to train Google's generative-AI models (Gemini and Vertex AI) — without affecting how Googlebot crawls the site for Google Search or AI Overviews. It is not a separate crawler; it is a control token Googlebot honors. The critical implication for AI-search access control is that Google-Extended, not Googlebot, is the correct lever for AI-training opt-out: disallowing Google-Extended stops model training while leaving Search and AI Overviews eligibility fully intact, whereas disallowing Googlebot removes the site from Google Search entirely. Confusing the two is one of the most expensive mistakes in the space — teams that block Googlebot believing it opts them out of AI Overviews instead delete themselves from organic Search. Apple's equivalent token is Applebot-Extended, which opts out of Apple model training while leaving Siri and Spotlight eligibility intact.