Google、検索結果でのAI生成サマリー表示が43%に増加

Google’s AI-generated summaries appeared in 43% of US searches measured by Similarweb, up from 15% a year earlier, according to the market intelligence firm’s 2026 Generative AI Landscape report.

AI Overviews display generated summaries within conventional Google results, while AI Mode provides a conversational interface for longer questions and follow-up prompts. Users can move from an AI Overview into AI Mode while retaining the context of their original search.

Google said AI Mode uses a technique called query fan-out, which divides a question into related subtopics and runs multiple searches. The system uses information from those searches to produce a response with supporting links.

Google expands conversational search

Similarweb estimated that visits to Google’s AI Mode web experience increased from 126 million in June 2025 to 279 million in May 2026. Google separately reported in May that AI Mode had surpassed one billion monthly users, although its figure covers users rather than web visits and is not directly comparable with Similarweb’s estimate.

The figures also measure different parts of Google Search. The 43% figure tracks the share of US searches displaying AI Overviews, while the AI Mode figures relate to activity within Google’s conversational search service.

Similarweb recorded a 5.4% increase in the average length of Google searches following the introduction of AI Mode. The report said users were entering longer, more natural-language searches similar to prompts used with AI assistants.

“People are now adopting a new, more natural way to search and discover,” Ethan Smith, chief executive of digital marketing firm Graphite, said in the Similarweb report.

Users can provide more detail in a single search instead of relying only on short keyword combinations. Google’s AI interfaces can respond to these longer searches and support additional questions without requiring users to open an external website immediately.

Similarweb said its estimates draw on first-party analytics, anonymised device information, external data partnerships, and publicly available web data. The company models those inputs to estimate traffic and user behaviour, meaning its figures are not direct counts supplied by Google or OpenAI.

According to the report, generative AI websites received an average of 9.5 billion monthly visits between June 2025 and May 2026, up 70% from the previous year. Monthly unique visitors increased 57% to 655 million, while mobile application downloads rose 58% to 4.4 billion.

Those figures cover the broader generative AI market, including standalone services such as ChatGPT, Gemini, Claude, and Perplexity. They provide context for Google’s expansion of AI within a search product that already reaches a wider internet audience.

Similarweb also found that most ChatGPT users continued to use Google. Audience overlap among ChatGPT, Gemini, and Claude indicated that people were using several search and AI services rather than moving exclusively to one platform.

Publishers have raised concerns about referral traffic when their content is incorporated into an AI-generated answer without producing a visit. Similarweb has previously identified news publishers among the sectors affected by changes in traffic from AI-based search tools.

Google has responded by changing how external sources appear within AI Overviews and AI Mode. In May, the company announced direct links within responses, article suggestions, website previews, and more prominent references to original material.

Google said the changes were intended to provide more information about linked pages and make relevant websites easier to identify. It did not release traffic data showing how the updates affected click-through rates to publishers or other external sites.

Citations do not always deliver traffic

Similarweb found that the share of ChatGPT responses containing web citations increased more than fivefold over the past year. The proportion rose from about 1.3% in June 2025 to 6.8% in May 2026, based on US desktop activity.

The measurement covers responses displaying source references, rather than the proportion of user prompts that caused ChatGPT to search the web. Citations also do not confirm that a user opened the linked source.

Citation rates varied by sector. Similarweb recorded higher rates for travel, retail, and sports responses, where information such as prices, availability, comparisons, and results can change frequently.

The firm also found a difference between the pages cited in AI responses and those receiving referral traffic. About 65% of URLs cited by ChatGPT were located two or three folders below the main domain, including articles, product pages, and other detailed content.

Folder-depth two alone accounted for 41.7% of cited URLs. By comparison, 58.8% of AI referral traffic landed on homepages.

The results indicate that the content used to support an AI answer and the page visited after a click often serve different functions. Detailed pages can supply information for a response, while displayed links can direct users to a company or publisher’s main website.

ChatGPT’s May 7 search update gave brand links greater prominence within generated responses. Similarweb recorded a 157.7% week-over-week increase in referral traffic following the update, while homepage referrals increased 354.7%.

The firm observed the increases after the interface change but did not establish that the update was solely responsible. The data covers ChatGPT referral activity and does not measure clicks from Google AI Overviews or AI Mode.

Before the update, about 26% to 32% of ChatGPT referral visits landed on homepages. The proportion increased to around 60% after May 7, based on desktop activity measured between April 30 and May 20, 2026.

The difference between cited sources and referral destinations gives publishers and website operators separate figures to track. Citation data measures which pages appear as sources, while referral data records where users arrive after clicking a link.

Cloudflare is also testing a Pay per Crawl service that allows participating website operators to permit, charge, or block individual AI crawlers. The private-beta programme allows publishers to set a fee that an authenticated crawler must pay before accessing content.

The system can return an HTTP 402 “Payment Required” response when paid access applies. Cloudflare records completed paid requests, charges the crawler operator, and distributes the proceeds to the website owner.

Cloudflare has also made configurable HTTP 402 responses available to paying customers through its AI Crawl Control service. Website operators can use the response to provide licensing terms or contact details to crawlers, while automated payments through Pay per Crawl remain in beta.

The measures add another option for publishers deciding how AI services can access their material as generated answers become more common across search and standalone AI platforms.

(Photo by Christian Wiediger)

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