Google-Extended: what blocking it actually does
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Short answer
Google-Extended is a robots.txt token that controls whether content Google crawls may be used to train Gemini models and to ground Gemini and Vertex AI responses. Google states explicitly that it does not impact a site's inclusion in Google Search and is not used as a ranking signal.
It is a control, not a crawler
Google-Extended does not fetch anything. There is no Google-Extended user agent arriving in your logs. Googlebot does the crawling, and Google-Extended is the token you use to say what may be done with what Googlebot already collected.
That is why the usual reasoning about blocking crawlers does not transfer. You are not turning off a fetch, you are setting a usage permission on a fetch that happens either way.
What Google says about ranking
Directly, in its crawler documentation: Google-Extended does not impact a site's inclusion in Google Search nor is it used as a ranking signal in Google Search.
That sentence is worth having to hand, because it is the single most common piece of misinformation in AEO advice sold to merchants. Blocking Google-Extended is not an SEO risk. It is also not an SEO tactic.
Google-CloudVertexBot is a different thing
The other Google token in this area is Google-CloudVertexBot, which Google describes as crawling sites at the site owner's own request in order to build Vertex AI agents. Google states it has no effect on Google Search or other products.
If you have not asked Google to build a Vertex AI agent over your site, this token has nothing to do with you.
Should a Shopify store block it
Blocking Google-Extended keeps your content out of Gemini training and out of Gemini grounding. Grounding is the part that matters commercially: it is how a Gemini answer gets anchored to real page content rather than model memory.
For a store that wants to be found by shoppers using Gemini, blocking it works against you. For a brand with copy it does not want absorbed, it is the correct and safe lever, and it costs nothing in Search. Either way, decide it on those terms and not on ranking fear.
How you actually change this on Shopify
Shopify generates robots.txt for you and there is no field in the admin for it. To change a rule you add a `robots.txt.liquid` template to your theme, which Shopify then renders instead of the default while still keeping its own future updates.
Shopify's help page is blunt about the risk: editing this file is an unsupported customization, Shopify Support will not help with it, and it says in as many words that incorrect use of the feature can result in loss of all traffic. Copy the default rules first, add your block, and read the rendered file at /robots.txt afterwards.
- Online Store, then Themes, then Edit code
- Add a new template called robots.txt.liquid
- Keep the default rules, then add your own user-agent group
- Load yourstore.com/robots.txt and read what actually rendered
Frequently asked questions
Does blocking Google-Extended hurt my Google rankings?
No. Google's documentation states that Google-Extended does not impact a site's inclusion in Google Search and is not used as a ranking signal. It governs Gemini training and grounding only.
Is Google-Extended a crawler?
No. It is a standalone product token used to control how crawled content may be used. Googlebot does the fetching, so you will not see Google-Extended in your server logs.
Does Google-Extended control AI Overviews?
Google documents Google-Extended as controlling Gemini model training and grounding in Gemini apps and Vertex AI. Google's Search features are governed by Googlebot and standard Search controls, which is a separate lever.
Sources
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