Gemini now tags its links with UTMs. The AI Overviews tag was a browser extension.

On 1 October 2026, Search Engine Journal reported that Gemini had started adding UTM parameters to the links it sends people to.

On 2 October, Search Engine Roundtable reported that Google was testing a tracking parameter on links inside AI Overviews and AI Mode.

One of those is real. The other was a browser extension.

Both landed in the same 48 hours, and both were shared as good news for anyone trying to measure AI referrals. So this post is about the change and about the checking.

It also corrects two older NovaTechRay posts, which I will get to.

1. What was reported about Gemini

The source is a Reddit thread, quoted in the SEJ piece. The poster said Gemini had started adding UTMs within roughly the previous day.

Google's John Mueller replied in the thread, as SEJ quotes him: "Nice. I see it too."

That reply is the strongest evidence there is. It is not documentation.

SEJ is clear on the gap. Google's implementation is undocumented, so nobody outside Google knows which answers trigger the tags.

SEJ also notes that ChatGPT tags only links in answers grounded in web sources, not answers drawn from training data. Gemini may behave the same way. Nobody has shown that it does.

People are already looking for this. Google autocomplete, checked on 3 October 2026, suggests "gemini utm source" for the query "gemini utm".

2. The parameter that was not Google

Here is the complication.

On 2 October, Barry Schwartz wrote up a LinkedIn post by Tom Pool showing ?st_source=ai_overview on links in AI Overviews, and screenshots of the same in AI Mode.

Schwartz said in the same piece that he could not reproduce it in several browsers.

Then came the update. Pool told him it was "a Chrome Browser Extension modifying the URLs", and Schwartz added that note to the top of the article.

So nothing was being added by Google. An extension was rewriting links on one person's machine, with screenshots that looked exactly like a Google test.

That one went the right way. A reporter tried to reproduce it, failed, and published the correction once the source found the cause.

Most claims about AI referral tracking never get that second step.

3. What I got wrong before

Two NovaTechRay posts made a claim that is now partly out of date.

Three corrections to every GA4 guide for tracking ChatGPT referrals says UTM tags cannot help, because you do not control the links inside an AI answer. The booking that never showed in analytics says the same thing.

The reasoning still holds for you. You cannot add a UTM to a link an assistant writes.

But the assistant can. SEJ reports ChatGPT already tags grounded links, and now Gemini is tagging some too.

So the accurate version is this: you cannot tag AI links yourself, and some assistants now tag a share of their own. The sessions with no referrer and no tag still land in Direct, and nothing recovers them.

I am adding a dated note to both older posts rather than rewriting them, so the earlier wording stays visible.

4. What a UTM fixes, and what it does not

A referrer is a header the browser sends. It gets dropped in app webviews, on some mobile flows, and when someone copies a link into a new tab.

A UTM lives in the URL itself. If the link is tagged, the tag arrives with the click, whether or not a referrer comes along.

That is why this matters more for Gemini than it sounds. Gemini lives inside a mobile app and inside the phone's assistant, which are the places referrers tend to go missing. SEJ quotes a Redditor making exactly that argument.

What it does not fix:

• Clicks on links Gemini does not tag. We do not know which those are.
• Mentions with no click. A business named in an answer that the reader then searches for by name shows up as branded search or Direct, never as Gemini.
• Answers the reader acts on offline. A phone call or a walk-in carries no parameter at all.

So treat Gemini-tagged sessions as a floor. The real number sits above it, by an amount nobody can measure yet.

5. How to confirm it in your own data

Do not copy a parameter value from a blog post, this one included. Read the value your own site receives.

1. Open the landing page report with query strings. In GA4, an exploration with the dimension "Page location" shows the full URL. Filter it for "utm_source" and look for anything naming Gemini.
2. Check your server logs if you have them. The UTM sits in the requested URL, so it is there even when analytics scripts are blocked.
3. Compare against the referrer. Sessions where the source is Gemini but the referrer is empty are the ones that would have been Direct last month.
4. Update your custom channel group. If your AI channel matches on referrer domain only, add a rule for the new source value you found in step 1.
5. Note the date you first saw it. Any trend line crossing 1 October now has a measurement change inside it. Annotate the chart so nobody reads it as growth.

At NovaTechRay we keep a dated change log next to every client's AI referral report for exactly this reason. Half the movement in these charts is the instruments changing.

6. How to check the next one before you believe it

This week gave a clean test case, so here is the routine.

• Can a second person reproduce it? Schwartz could not, and that was the first sign.
• Is it in a clean browser? Repeat it in a fresh profile with every extension off. Extensions rewrite links far more often than people assume.
• Has the platform said anything? For Gemini, a Google employee confirmed seeing it. For the AI Overviews tag, nobody from Google said a word.
• Does it show in data, or only in screenshots? A tag that is real appears in landing page URLs across many visits, from many devices.

If you also run social accounts, the same discipline applies to which platforms reach AI answers at all. VALORAE Media checked that against each platform's own documentation in Your Reels don't show up in ChatGPT. Your YouTube videos do.

The short version

• Gemini started adding UTM parameters to some outbound links around 1 October 2026, per SEJ, and Google's John Mueller said he saw it too.
• Google has not documented which links get tagged.
• The st_source=ai_overview parameter reported on 2 October came from a Chrome extension, not Google.
• You still cannot tag AI links yourself. Some assistants now tag their own.
• Read the parameter value from your own landing page URLs, then update your channel group to match.
• Annotate every AI referral chart at 1 October.
• Before believing a tracking claim, reproduce it in a clean browser.

This is the measurement work NovaTechRay does at novatechray.com.