Gemini's new link tag is a step, not growth

A tracking-tag launch is a measurement change, which means the traffic it reveals was already arriving and is only now being labeled.

That distinction matters this month. Around the end of September 2026, Google started adding UTM parameters to some outbound links in Gemini answers. Search Engine Journal reported the change on October 1 after a Redditor in r/SEO noticed the tags. Google's John Mueller replied in the thread that he could see them too. There is no announcement and no documentation. SEJ describes the implementation as undocumented, and the conditions that trigger the tag are unknown.

For anyone reporting on AI referrals, the practical effect is easy to predict. The first weeks of October will show more sessions attributed to Gemini than September did. Some of that is real growth. Much of it is likely to be visits that used to land under "direct" or under a plain referral row, now moved into a clearly labeled one.

#Where Gemini visits were sitting before

Before the tag, a Gemini click reached your analytics in one of two ways. If the browser passed a referrer, the session showed up as a referral from a Gemini hostname. If it did not, the session had no source at all and was counted as direct. We covered that second path in AI traffic shows up as direct.

How much fell into each bucket depended on the surface. In the Reddit thread SEJ quotes, one commenter said the referrer "mostly survives on desktop web only", claimed pass-through from the Gemini mobile app was around 9 percent, and said Android assistant invocations strip it entirely. Those are one person's observations, not a measurement Google has confirmed, and SEJ presents them that way. They still describe the mechanism well: the share of Gemini clicks you could see before depended on device mix, and some of it was invisible.

A UTM parameter travels in the URL itself, so it does not depend on the browser sending a referrer. In Google Analytics 4, UTM values populate the manual source and medium dimensions, and they arrive as part of the landing page URL. Where Gemini adds the tag, a visit that previously looked like direct traffic can now carry a Gemini label.

#Why the chart will mislead

Put those two facts together and the shape of the next report is clear. The Gemini line steps up at the end of September. The direct line on the same landing pages steps down by some amount. Total sessions to those pages barely move.

A team that reads only the Gemini line will report growth that did not happen. A team that reads only the direct line may think it lost brand traffic. Both readings come from the same cause: the label changed, not the visitors.

There is also an asymmetry to watch. Because the trigger conditions are unknown, the tag may not be on every Gemini link. Some clicks will still arrive with a referrer and no tag, and some will still arrive with neither. Gemini traffic is now spread across three rows (tagged, referral only, and unlabeled), and the tagged row is the only new one.

ChatGPT went through a similar change earlier, with one difference. OpenAI's publishers and developers FAQ documents that ChatGPT adds utm_source=chatgpt.com to referral URLs. A documented parameter can be written into a channel rule with some confidence. An undocumented one can change format, scope, or disappear without notice.

#What to do with October's data

Annotate the break. Add a note to your analytics and dashboards at September 30, 2026, labeled as a Gemini tagging change. Anyone comparing September to October needs to see it before they read the chart.

Report Gemini as a combined figure. Sum tagged Gemini sessions and Gemini referral sessions into one number, and keep the two components visible underneath. Growth in the combined figure is closer to real demand than growth in the tagged row alone.

Watch direct traffic on the same pages. Pick the landing pages that receive the most Gemini sessions after the change and compare their direct sessions before and after. A drop in direct that roughly matches the rise in tagged Gemini traffic is relabeling. A rise in tagged Gemini traffic with flat direct traffic is more likely new visits.

Match on the source loosely. Google has not published the parameter values. Write the channel rule to catch any source value containing "gemini" rather than one exact string, and review it monthly. Check the actual values in your own data before you rely on them, as we argued in check who wrote the tracking parameter.

Keep raw URLs in your server logs. GA4 shows you the dimensions it parsed. Your web server logs keep the full request line, including the query string. If Google changes the tag format, the logs let you rebuild the history.

Do not tag your own links with it. Adding a Gemini-looking UTM value to your newsletter or social links would mix your own campaigns into the Gemini row. Keep that value reserved for traffic Gemini actually sends.

Compare against visibility, not just clicks. Referral counts tell you how many people clicked. They say nothing about how often Gemini cited your pages without a click. Pair the referral figure with citation tracking for the same topics so a tagging change cannot be mistaken for a change in how often you appear.

#The general rule

Every new attribution signal creates a step in historical data. The step looks like a trend because it shows up in the same chart as real trends. The fix is the same each time: find the date, find where the traffic used to be counted, and report the sum across old and new labels until there is enough history on the new one to stand alone.

Gemini's tag is useful. It makes some previously invisible clicks visible, and because it lives in the URL, it does not depend on the app passing a referrer. Treat the first month of tagged data as a calibration period, and keep the claim in your reports limited to what changed: the label, and some share of the visits behind it.