AI Assistants Hit 76 Billion Monthly Sessions as Report Drops Search Comparison

Six AI assistants recorded 76 billion sessions worldwide in September, up 37% year over year, according to Graphite's updated AI usage report. Unlike the agency's March edition, the new report drops its headline comparison between AI usage and search engines entirely.

The retreat is a data problem, not a demand story. In March, Graphite put monthly AI sessions at 56% of search volume worldwide and 34% in the U.S. The November report states that edition likely undercounted Google search use from the Google Android app, and the agency says it "can no longer reliably compare" AI search usage with search engines.

The session figures come from Similarweb estimates of web visits plus mobile app sessions. Desktop apps are excluded because, as the report explains, no reliable data exists for them. Graphite sells SEO and AEO services; Similarweb sells the data.

What changed since March?

The March report counted search engine usage from website visits only, on the assumption that apps saw little use. The new edition contradicts that assumption. The Google Android app alone accounts for an estimated 11.8 billion monthly sessions in the U.S., used for image recognition, translation, Google Discover and general search.

Graphite says it has "no reliable data source" to determine what share of those sessions involve general search. The March report's 56% figure, and its estimate that ChatGPT accounted for 20% of global search-related traffic, both relied on the web-only count. The November report does not revisit either number, yet the March page still highlights them as major findings, with a link to the new report at the top.

How much traffic does AI actually send?

For practitioners, the referral numbers are the hard constraint. The report's data "suggest that AI accounts for less than 1% of traffic on average" to websites. A chart of U.S. traffic in the second quarter of 2026 puts organic search at 49 times the volume of AI referrals, and paid search at eight times.

Growth is fast but from a small base. AI referral traffic rose 92% year over year worldwide as of July, and 75% in the U.S. The referral figures cover the top 43,000 sites among domains with at least 100,000 monthly U.S. visits in six or more months between July 2023 and July 2026.

ChatGPT dominated those referrals. In July it accounted for 60% of AI referral traffic worldwide, followed by Gemini at 14% and Claude at 10%. In the U.S., ChatGPT's share was 66%, with Claude at 11% and Gemini at 10%.

How did usage grow?

The growth curve has two distinct phases. Between July and December 2025, global session activity across the six assistants rose just 2.3%, which the report describes as a plateau. From January through September 2026, activity climbed 19%. Year-over-year U.S. growth hit 45% in September.

ChatGPT grew 24% year over year worldwide and represented 58.9% of all sessions added. Claude posted the largest percentage gain globally at 1,901% and generated 26% of additional sessions. Perplexity was the only assistant of the six to decline, falling 27%.

Mobile dominates. Mobile app and mobile web accounted for 89% of global sessions in the third quarter of 2026, and 78% of U.S. sessions.

What does this change for channel planning?

The report's retraction exposes how fragile the AI-versus-search ratio really is. OpenAI claimed ChatGPT receives roughly one-fifth as many search-like queries as Google, but did not include the Google Android figure in that calculation. The two estimates also count different things: OpenAI logs a search whenever a question sends ChatGPT to the web, while Graphite counts website visits and app sessions. Before any AI-to-search ratio enters a channel plan, check how its source counted Google.

Graphite also cites anecdotal evidence that some visits prompted by AI answers get credited to direct visits or branded search, which referral reports would miss. Its early numbers suggest branded search traffic is roughly flat year over year, with full results to come. For comparison, Similarweb's June data found that among people who visited a brand's site after a ChatGPT recommendation, 55.9% of that traffic arrived through branded search, in U.S. desktop data.

Expect the measurement debate to intensify as AI referral growth outruns the tools built to track it.