Similarweb's 2026 Generative AI Landscape report, authored by Laurie Naspe and Sam Sheridan, documents a sharp decline in ChatGPT's share of standalone web visits since mid-2024, while advertising appeared in 26% of US desktop ChatGPT chats during June 2026. Average monthly web visits to generative AI platforms reached 9.5 billion between June 2025 and May 2026, up 70% from 5.6 billion, and monthly unique visitors climbed 57% to 655 million from 418 million. App downloads showed a discrepancy: the summary cites 2.7 billion downloads, up 134% year over year, while a detailed chart shows 4.4 billion downloads against 2.8 billion, a 58% increase. ChatGPT's share of chatbot website visits fell from above 80% through late 2024 to just above 50% by May 2026, with Gemini, Claude, Perplexity and DeepSeek absorbing the difference. By US monthly active users between June 2025 and May 2026, ChatGPT grew 87%, Gemini 31%, Meta AI 435%, Grok 117%, Perplexity 94% and Claude 349%, while Microsoft 365 Copilot fell 31% and DeepSeek fell 23%. Similarweb measured 494 million ChatGPT users worldwide between March and May 2026, of whom 95% also used Google; Gemini reached 310 million and Claude