Google appears to be testing a URL tracking parameter that would let publishers identify clicks coming from AI Overviews and AI Mode in Search. Tom Pool, who first spotted the test, reported seeing the parameter ?st_source=ai_overview appended to links cited within AI Overviews across multiple examples.

Pool posted his findings on LinkedIn and wrote: "Just started seeing the ?st_source=ai_overview parameter on links mentioned within AI Overviews – is this the start of actual proper attribution reporting?"

This matters because publishers and SEOs currently cannot reliably separate AI Overview clicks from ordinary blue-link clicks in their analytics. Traffic from AI Overviews and AI Mode arrives looking like standard organic Search referrals. A dedicated parameter at the URL level would change that, giving site owners a direct signal in server logs and analytics platforms whenever a visitor arrives from an AI-generated answer rather than traditional web results.

The parameter reportedly appears in the AI Mode version as well, and Pool said it shows "even in the links mentioned in the source list too" — meaning both the inline citations inside the AI answer and the supporting source list may carry the marker.

There is a significant caveat. Attempts to replicate the sighting across several browsers failed. The parameter did not appear in testing, which suggests Google is running this as a limited experiment or bucket test rather than a full rollout. Nothing is confirmed: Google has not issued any statement about the parameter, and its visibility so far rests entirely on Pool's screenshots and reports.

A complication: the black hat angle

The picture grew murkier after the initial report. An anonymous source later claimed the sightings may not be a Google test at all. According to that source, this is a black hat tactic in which practitioners force Google to index parameterized URLs at scale, deliberately injecting ?st_source=ai_overview into URLs to measure exactly which clicks originate from AI Overviews.

If that explanation is correct, the parameter originates outside Google — SEOs gaming the index for attribution data rather than the search engine shipping an official reporting feature. That would make this a case of tool-signal confusion rather than a confirmed product change.

Right now, both explanations remain on the table: either Google is quietly testing first-party AI Overview attribution, or third parties are manufacturing the signal themselves. Google has confirmed neither.

What this means for publishers

The demand driving both scenarios is real. Publishers, news sites, and content-driven businesses have struggled to quantify AI Overview impact since Google launched the feature, because lost or gained clicks from AI answers blend invisibly into overall organic traffic. An official URL parameter would be the cleanest solution proposed so far — no log-file inference, no third-party click modeling required.

E-commerce and affiliate sites, which depend heavily on precise channel attribution for budget decisions, would benefit most from a verified parameter. News publishers tracking referral quality would gain a direct measure of how much traffic AI Overviews actually send.

Until Google confirms anything, site owners should treat any ?st_source=ai_overview entries in their logs with suspicion. They may reflect a genuine Google experiment — or they may reflect someone else's attribution scheme aimed at the same data you want.

Watch whether the parameter appears in wider testing, whether Google comments on it, and whether it eventually shows up consistently across AI Overviews and AI Mode for all users. A confirmed, stable rollout would signal that Google is finally building first-party AI answer attribution into Search itself.