What is Google-Extended?
Google-Extended is a robots.txt token that controls whether Google may use a site for Gemini training and grounding. It does not affect Google Search.
Google-Extended is not a crawler. Google says it "doesn't have a separate HTTP request user agent string." Crawling is done by Google's usual crawlers, and the token is read in robots.txt "in a control capacity." It covers whether content may be used for "training future generations of Gemini models" and for grounding in Gemini Apps and Grounding with Google Search on Vertex AI.
Disallowing it does not remove a site from Google Search: Google says it "does not impact a site's inclusion in Google Search nor is it used as a ranking signal." It also decides Gemini Apps grounding: Google says "websites that specifically allow Google-Extended are eligible to appear in responses and receive clicks via grounding in Gemini Apps." Google also plans, in 2027, to read the shared __usage_ai-training opt-out as a Google-Extended disallow when Google-Extended is not named in the file.
Why does it matter to your business?
Google-Extended is the one switch for both Gemini training and Gemini Apps grounding, so blocking it to refuse training also gives up that grounding.
Sources, verified October 31, 2026
Want to know how your site measures up?
The free audit checks whether Google and AI answer engines can find, understand, and quote your pages.