Start with Google's own words. Per the crawler documentation, "Google-Extended is a standalone product token that web publishers can use to manage whether content Google crawls from their sites may be used for training future generations of Gemini models that power Gemini Apps and Vertex AI API for Gemini and for grounding (providing content from the Google Search index to the model at prompt time to improve factuality and relevancy) in Gemini Apps and Grounding with Google Search on Vertex AI."
Two things follow, and they are the practical answer for publishers.
First, Google-Extended really does control something here. It gates whether your crawled content trains future Gemini models, and whether it can be used to ground a live answer in the Gemini app. That is a genuine, documented lever.
Second, and this is where it differs from everything on our Search hubs: Google-Extended does not gate whether you appear in an AI Overview or an AI Mode answer. Those run on ordinary Search indexing. So a publisher can disallow Google-Extended, keep full Search and AI Overviews eligibility, and still stop their content training Gemini or grounding its chat answers.
Google is explicit that the token costs you nothing in Search: it "does not impact a site's inclusion in Google Search nor is it used as a ranking signal in Google Search". It also runs no crawler of its own. As the documentation puts it, "Google-Extended doesn't have a separate HTTP request user agent string. Crawling is done with existing Google user agent strings; the robots.txt user-agent token is used in a control capacity."
What it cannot do is remove you from a conversation entirely. It restricts Google's use of its own crawled copy, so it does not govern what happens when a user pastes your URL into a chat directly. No documentation describes a separate mechanism for that case.
Whether Gemini links out, and how much traffic it sends
Gemini does cite, but not always. Google's help page says "When sources are available, you can find the Sources button at the bottom of the response or in-line throughout the response", and equally that "Not all responses include related links or sources."
One case is guaranteed: "If Gemini Apps directly quotes a large amount of text from a webpage, you'll see a link to that webpage in the sources list."
There is a distinction in that documentation worth holding onto. Google also surfaces "related links", which it says are "not necessarily sources used to generate the response". A link sitting next to an answer is not proof Gemini used that page for the claims it made.
On volume, Statcounter is the verified backbone: Gemini reached 8.65% of AI assistant referrals to websites in March 2026 and 9% in April, second behind ChatGPT. Note that this is share of a pool rather than absolute traffic, and that it measures referrals out to sites rather than usage of the assistant itself.
Figures we deliberately do not print. A set of Gemini referral numbers circulates widely in SEO coverage (+115% in two months, 29% more visitors than Perplexity) attributed to a panel of 101,000 sites. No fetchable primary report exists for them, so they stay off this page until one does.
