If you can only optimize for one AI chatbot, the traffic data says which one: ChatGPT sent 92.4% of all referral traffic from standalone AI platforms in the 19 months through May 2026, according to the third edition of Previsible’s AI Traffic Study — and ecommerce was the fastest-growing category of that traffic.

The numbers

Previsible tracked 6.77 million LLM-driven sessions across 166 production GA4 properties — spanning SaaS, ecommerce, finance, legal, health, insurance, education and publishing — from November 2024 through May 2026 (Previsible; Search Engine Land). Monthly LLM-referred sessions grew roughly 9.9x over the window, reaching 644,478 in May 2026.

Within that traffic, the standalone-chatbot field looks like a single-vendor market:

  • ChatGPT: 92.4% of standalone-LLM referral traffic, growing about 12.8x since the study began, with “no sign of slowing.”
  • Gemini: #2 and rising, up 3.2x (from 5,598 to 18,119 monthly sessions).
  • Claude: the fastest mover, up roughly 64x (from 133 to 8,528 monthly sessions) and passed Perplexity in March 2026 — notable given Claude was reportedly under 1% of referral share as recently as Previsible’s December 2025 edition.
  • Perplexity: down ~61% from its March 2025 peak.
  • Copilot: down ~96% from its August 2025 peak (8,651 sessions) to 339 sessions in May 2026 — functionally noise.

Ecommerce is where it’s growing fastest

Across the 166 sites, ecommerce referral traffic from AI platforms rose roughly 37x over the study window, as shoppers increasingly land on product pages with intent already formed rather than arriving to browse. For a merchant deciding where to spend limited AEO effort, that’s the headline pairing: the fastest-growing referral channel and the most concentrated one land on the same platform.

The number that should temper all of this

Previsible and Search Engine Land both flag that AI-influenced traffic surfaced inside Google itself — AI Overviews and AI Mode — almost certainly exceeds all standalone-LLM referral traffic combined, but isn’t in this dataset because AI Overviews mostly don’t generate attributable click-through sessions the way a standalone chat app does. The 92.4% figure describes dominance within a shrinking slice (standalone chat apps) of a bigger, less-measurable pie (all AI-mediated discovery). A store fixated on ChatGPT referral tracking alone is still blind to where more of its AI-driven traffic likely already sits.

What this means for merchants

Traffic share answers “where should I instrument and optimize retrieval first” — and right now that’s ChatGPT, distantly followed by Gemini, with Claude worth watching for technical-buyer categories. But a referral session is not a sale. AgentReady’s own research has already made this point about Google’s AI shopping metrics: a platform showing you traffic, or citing your product, is a discovery signal. It says nothing about whether the agent that landed on your page can actually resolve price, stock and shipping and complete checkout once it’s there. If ChatGPT is about to be 92% of your AI-referred visits, the question worth answering isn’t just “can ChatGPT find me” — it’s whether that session can convert once an agent lands on your product page.

Sources

Traffic share tells you where an agent finds you. AgentReady audits whether it can buy once it’s there.