A parameter on AI Overview links looked like Google adding attribution. The report was corrected: it was a browser extension. What to check in your own data.
On October 2, 2026, Search Engine Roundtable reported that Google seemed to be testing tracking parameters on links inside AI Overviews and AI Mode. The parameter was ?st_source=ai_overview, and it would have given publishers a clean way to separate AI Overview clicks from ordinary organic ones. The same article now says otherwise.
What the report says
The Search Engine Roundtable article by Barry Schwartz opens with "Google seems to be testing adding tracking parameters to the link URLs within AI Overviews and AI Mode." An update added later reads "This was a browser extension - not Google." The article says the parameter is appended to the end of the link, and that the author tried to replicate it in several browsers but was unable to. It says a reader saw it in several examples, including links in the source list.
We did not find which extension added the parameter, and the article does not say. Any motive for an extension doing this would be a guess.
Why one sighting and one failed reproduction matters
Our view: one person seeing a parameter consistently while a second person cannot reproduce it points to a cause on the first person's browser, not on Google's servers. That is why the standard check is to try the same search in a clean browser profile. The original article flagged its own failed reproduction, which made the later correction easy.
What it means for your referral data
If a browser extension can append a parameter to outbound links, pages that those users click through to will see that parameter in the URL. We have no data on how many people run such an extension. The risk is reading a third-party tag as first-party attribution. It would make AI Overview traffic look measurable when it is not.
Referral data can be altered in other ways too. See our posts on how Google's goto passthrough links changed how rank trackers and backlink tools read result URLs and how agentic browsers strip or rewrite referrers differently by product. Each has a different cause, and each makes the same point: the URL that reaches your server has passed through steps you do not control.
What to check on your own site
Search your analytics for landing-page URLs containing st_source and see whether any sessions carry it. If they do, check whether they cluster on a few user agents or devices, which would fit an extension better than a platform change. If nothing shows up, that is also a result. We found no Google announcement of a tracking parameter for AI Overviews while writing this, so until one exists, treat clicks from those links as mixed in with the rest of organic traffic and do not build an attribution rule on a parameter that one person's screenshot suggests.
