By the Mayab Media Team
If you built a GA4 report around utm_source=gemini in October, check it today. It has probably been flat for a month.
In September, Google's Gemini started adding that tag to the website links it cites in answers. SEOs noticed, Google's John Mueller replied on Reddit that he could see it too, and plenty of people (us included) were glad to finally get a clean label for AI traffic. Then it stopped. On October 30, Search Engine Roundtable reported that the parameter is gone. Data shared by the consultant Natzir showed tagged visits climbing for roughly three weeks and then dropping to nothing overnight, around September 28.
Google never documented the tag, and it hasn't explained why it disappeared either.
Where the visits went
Not all of them went missing. That's the good news.
Gemini on desktop, in a browser, still passes a referrer. According to Natzir's numbers, visits arriving with gemini.google.com as the referrer held steady the whole time, before, during and after the UTM experiment. If you've already got a channel rule that catches that domain, your desktop numbers are fine.
The iPhone app is the problem. Natzir's test found that the Gemini iOS app opens links inside its own built-in browser and sends no referrer at all. GA4 sees a visit with no source, no medium and no campaign, so it files it under Direct. The only fingerprint left is a "GeminiiOS" string in the user agent, which shows up in your server logs. GA4 standard reports won't show it to you.
So the tag was briefly patching a hole, and now the hole is back.
Why we'd care (and why we wouldn't panic)
For most small and mid-sized businesses, Gemini referrals are a small slice of total traffic. A few dozen sessions a month is common for a local service business. Losing the label on some of them won't wreck your marketing decisions this quarter.
What it does wreck is the trend line. Say your report showed 40 Gemini sessions in August, 95 in September and 50 in October. That looks like Gemini cooled off on you. It probably didn't. You likely lost the tag on the mobile share and kept only the desktop referrals. Make a budget call off that chart and you'd be reacting to a tracking change, not a change in demand. Easy mistake to make.
There's a second, sneakier effect. Direct traffic tends to look great in GA4, with high engagement and good conversion rates. When AI visitors who already know what they want get dumped into Direct, they inflate the "brand" story and hide the AI story. Nobody notices until someone asks why Direct grew 15% with no new brand campaign.
What we'd set up this week
None of this is hard, and most of it is cleanup you'd want to do anyway.
- Build an AI channel on referrers, not UTMs. In GA4 go to Admin, then Data display, then Channel groups, and create a custom group (copy the default one first). Add a channel called "AI Assistants" that matches session source against a regex like
gemini\.google\.com|chatgpt\.com|perplexity\.ai|copilot\.microsoft\.com. Put it above Referral in the order, or it'll never fire. - Keep
utm_source=geminiin the rule anyway. It costs nothing, and if Google turns the tag back on you'll catch it automatically. - Annotate September 28. Drop a note on your reports saying Gemini UTMs stopped around then. Future you will thank present you.
- Watch Direct on mobile landing pages. Filter Direct sessions to iOS and look at which deep pages people land on. Somebody typing your URL lands on the homepage. Somebody landing directly on a three-year-old blog post about water heater sizing probably clicked a link somewhere.
- Ask your developer about logs. If your host keeps raw access logs, a simple count of requests containing "GeminiiOS" gives you a rough monthly number. It's crude, but it's real.
We'd skip anything that tries to "fix" this with fingerprinting scripts or paid attribution add-ons. The signal is too small to justify the cost or the privacy headache.
The bigger lesson about AI attribution
Platforms change how they pass data whenever it suits them. Gemini added a tag without telling anyone and removed it the same way. Expect the other assistants to behave no differently. If your AI reporting depends on one parameter from one vendor, it will break again.
Referrers, landing page patterns and a quick "how did you hear about us?" field on your forms are boring. They also survive these changes. A lead form that asks the question gives you something no tag can: the customer's own answer.
Treat AI traffic numbers as directional for now, and build your tracking so one vendor's quiet change can't erase it.
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