In short
ChatGPT sends by far the most AI referral traffic, with Perplexity a distant second and the rest barely registering. For most sites AI referrals are still under a few percent of visits, but they are growing fast and convert unusually well. Clicks from Google's AI Overviews do not count; they arrive as normal organic.
Key points
- ChatGPT dominates AI referrals for almost every site that receives any.
- Total volume is small, typically low single digits of traffic, but growth is steep.
- Visitors arriving from an AI answer are pre-qualified by it, and tend to convert well.
- Google's AI surfaces are invisible here. Their clicks land as ordinary google organic.
- Measure it with one GA4 segment on referral hostnames. Ten minutes, once.
The short version
If your site gets AI referral traffic at all, most of it is ChatGPT. Every published breakdown and every client property I have looked at agrees on that ordering: ChatGPT first by a wide margin, Perplexity a distant second, Gemini, Copilot and Claude sharing the leftovers.
The volumes are honest-small. For a typical site, AI referrals are somewhere under a few percent of total visits in 2026, against the majority that classic search still delivers. Two things stop that being a reason to ignore it: the growth curve, referrals multiplying year over year while organic clicks flatten, and the quality, because a visitor who clicks through from an answer has already read a summary of you and come anyway.
Where the visits come from
| Source | Referrer you will see | What to expect |
|---|---|---|
| ChatGPT | chatgpt.com | The bulk of AI referrals, often with utm_source=chatgpt.com attached |
| Perplexity | perplexity.ai | A distant second, skews research-heavy queries |
| Gemini | gemini.google.com | Small; its links are less prominent |
| Copilot | copilot.microsoft.com | Small outside Microsoft-heavy audiences |
| Claude | claude.ai | Smallest of the five today |
Treat the ordering as durable and the gaps as perishable. Product changes, a links redesign in one app, move these shares overnight.
The counting trap
Google's AI surfaces never appear in this list. A click from an AI Overview or from AI Mode carries a normal Google referrer and lands in your analytics as organic search, blended in with classic results. The platform reshaping search most is the one you cannot see doing it.
So keep the two ledgers apart. AI referrals, the chatgpt.com and perplexity.ai visits, measure the assistants that link out. Google's AI effect shows up somewhere else entirely: in Search Console, as impressions holding while CTR slides, which the AI Overviews page walks through. Adding a ChatGPT segment tells you nothing about AI Mode, and mixing the two produces confident nonsense.
Set up the measurement once
In GA4, ten minutes:
- Reports, Acquisition, Traffic acquisition, then filter session source by chatgpt.com, perplexity.ai, gemini.google.com, copilot.microsoft.com and claude.ai.
- Save it as a comparison or an exploration segment named AI referrals.
- Add conversions and engagement to the report, because the interesting number is quality, not count.
- Note the month's figures somewhere durable. The value of this data is the trendline, and the trendline needs a start date.
Expect undercounting. Visits from inside apps sometimes arrive with no referrer at all and hide in direct. The segment is a floor, not a census.
What the traffic is like
The consistent finding, across published studies and my own client data: AI referral visitors behave like people who know why they came. They saw your name inside an answer, chose to click past it, and arrive with context. Engagement and conversion rates typically beat organic averages, sometimes by multiples.
Which reframes the small volume. A channel delivering one percent of visits at several times the conversion rate is not a rounding error, it is a qualification filter. The citation did the persuading before the click happened.
When this does not apply
If your business is local walk-ins or a brand people reach directly, AI referrals will stay negligible and this measurement is a curiosity. And if your AI referral count is currently zero, the fix is not referral optimisation, it is the visibility work everywhere else in this course: you cannot receive clicks from answers you are not cited in.
FAQ
Which AI platforms send the most referral traffic? ChatGPT, by a wide margin, for almost every site that receives AI referrals at all. Perplexity is a distant second, with Gemini, Copilot and Claude each contributing small shares. The ordering has been stable even as the totals grow quickly.
How much traffic does ChatGPT send to websites? For most sites, ChatGPT referrals are a small share of total visits, commonly under a few percent, though steeply up year over year. Sites frequently cited in answers within their niche see materially more, which makes citation visibility the input and referrals the output.
How do I see AI traffic in GA4? Filter or segment session source by the AI referrer domains: chatgpt.com, perplexity.ai, gemini.google.com, copilot.microsoft.com and claude.ai. ChatGPT also appends utm_source=chatgpt.com to many outbound clicks. Save the segment once and review it monthly with conversions attached.
Does Google AI Overviews traffic show as AI referral? No. Clicks from AI Overviews and AI Mode carry ordinary Google referrers and are counted as organic search, indistinguishable from classic results in analytics. Google's AI effect is visible only indirectly, as impressions holding steady while click-through rate falls in Search Console.
Is AI referral traffic worth optimising for? Not directly, because you cannot optimise the referral itself. It is the downstream result of being cited in answers. The visibility work, access, citable content, identity, is the lever; referral traffic is one of the places its results become measurable.
Do AI referral visitors convert? Generally well. Published analyses and client data point the same way: visitors arriving from AI answers engage more and convert at higher rates than average organic visitors, because the answer pre-qualified them before the click. Judge the channel on conversion quality, not visit count.
Why is my AI traffic so small? Because the channel is genuinely small for almost everyone in 2026, because in-app visits often hide in direct traffic with no referrer, and because referrals require citations first. Small and growing is the normal state. Zero, on a site with real content, usually points at a visibility problem worth auditing.
Sources
- Similarweb analyses of AI platform referral share, 2025
- Published GA4 measurement guidance from the major analytics blogs on AI referrer segments
- Client-side GA4 data informing the qualitative claims about conversion quality, anonymised
- First published.