Google-Extended does not control AI Overviews
Blocking Google-Extended will not take you out of AI Overviews. It is the single most repeated piece of wrong advice in this subject and it costs nothing to get right.
Checkable · read your own robots.txt
What Google-Extended actually governs
It is a robots.txt token controlling whether your content is used for training Google's models and for grounding Gemini. That is its scope. It is not a switch that removes you from the summary at the top of a results page.
What controls AI Overviews
Ordinary Google indexing. An AI Overview is assembled from pages in Google's search index, so the control that would remove you from it is the same one that removes you from Google search altogether. There is no setting that keeps your ordinary listings and opts you out of the summary above them.
That is an uncomfortable answer and it is the true one. The choice is not between appearing in results and appearing in summaries. It is between being in Google and not.
Why the confusion is expensive
Contractors have been advised to block Google-Extended to protect their content from AI, have done it, and have then been puzzled that the summary above their listing did not change. Meanwhile, depending on how the block was written, they may have removed themselves from Gemini's grounding, which is a surface they were trying to appear in.
The failure mode is a plausible-sounding instruction producing an effect nobody wanted, in a file nobody rechecked.
How to check in two minutes
Open yoursite.com/robots.txt. Look for Google-Extended and read whether it is allowed or disallowed. Then look for a blanket disallow, which covers everything including crawlers you meant to permit. Write down what you find before anyone edits it on your behalf, so there is a record of what changed and when.
Then decide deliberately. Blocking Google-Extended is a legitimate choice about training and grounding. It is simply not the choice most people think they are making. The full crawler list is here.