Which AI search engine sends the most referral traffic?

What the public data shows#

ChatGPT sends more referral traffic than every other AI assistant combined. Prefer’s GA4 connection shows whether that holds for your own site. The clearest public benchmark comes from Conductor, whose data across ten major industries (reported by Digiday in late 2025) put ChatGPT at roughly 87% of all AI referral traffic. ChatGPT referrals were also up about 52% year over year in Similarweb’s figures. Gemini is growing faster in percentage terms, but from a much smaller base, and Perplexity trails both.

Two honest caveats belong right next to that number:

• The whole channel is small. Across those same industries, AI assistants drove only about 1% of overall web traffic. ChatGPT leads a channel that is still a sliver of most sites’ visits.
• Aggregates are not your site. An 87% industry share is a useful backdrop, not a promise about your traffic. A developer tool, a local restaurant, and a B2B SaaS brand will each see a different mix depending on where their buyers ask questions.

So the headline answer is ChatGPT, clearly. The useful answer is: measure your own.

How to measure your own AI traffic#

The only referral figure that describes your site is the one in your analytics. You can build it with tools you already have:

• Segment the assistant referrers. Create a source segment for chatgpt.com, perplexity.ai, gemini.google.com, copilot.microsoft.com, and claude.ai. That isolates AI-driven sessions from the rest of your traffic.
• Use ChatGPT’s own tag. ChatGPT appends utm_source=chatgpt.com to the links it sends, per OpenAI’s Publishers and Developers FAQ, so its referrals are easy to pick out cleanly.
• Read referrals as the tail, not the whole channel. Because few users click a link inside an AI answer, the referral count understates AI search. Most of the influence happens inside the answer, unclicked, where your brand is either cited or absent.

Put those together and you get an honest picture: ChatGPT is the biggest AI referrer, the channel is small but high-intent and growing, and your own numbers are what you should plan against. For the full method, see our guide to measuring AI search ROI, and our AI search statistics page for the wider adoption numbers. To see which engines cite your brand in the first place, run a free AI visibility audit.

Sources

1. Conductor data across 10 major industries, reported by Digiday in late 2025, found ChatGPT accounted for about 87.4% of AI referral traffic; ChatGPT referrals also rose 52% year over year in Similarweb figures, while Gemini grew fast from a smaller base. Digiday, state of AI referral traffic 2025 (Conductor + Similarweb data)
2. The same reporting put AI assistants at only about 1% of overall web traffic across major industries, so even the leading engine sends a small volume today. Digiday, state of AI referral traffic 2025 (Conductor data)
3. ChatGPT appends utm_source=chatgpt.com to referral URLs, per OpenAI's Publishers and Developers FAQ, which lets you segment and measure your own AI referral mix in analytics. OpenAI Help Center, Publishers and Developers FAQ
4. Prefer, our product, connects to Google Analytics (GA4) and Google Search Console from its Starter plan, and tracks citations and mentions of your brand in ChatGPT, Gemini, Perplexity, Google AI Overviews and Google AI Mode. Prefer pricing (our product)