Similarweb Launches AI Ads for ChatGPT, Google AI Placements

Similarweb has launched AI Ads, a new Ad Intelligence dataset designed to provide advertisers with visibility into ad placements on conversational AI platforms like ChatGPT, Google AI Mode, and Google AI Overviews [1]. This release addresses a gap in transparency, as these platforms currently lack public ad libraries, making it difficult for advertisers to track their own campaigns or analyze competitors' strategies [2].

Uncovering AI Ad Placements

Similarweb's AI Ads dataset allows customers to conduct competitive analysis of advertising on ChatGPT, Google AI Mode, and Google AI Overviews across global and specific markets [1]. The company reports that 26% of ChatGPT responses, shown to users in the Free and Go tiers, already include sponsored ads [1]. Additionally, nearly 30% of ad-eligible Google AI Mode queries display ads, and over 40% of Google searches now trigger an AI Overview, which often contains ads [1].

Unlike established ad channels such as Meta's Ad Library, Google's Ads Transparency Center, or TikTok's Creative Center, these AI environments do not offer a public record of ad activity [2]. This lack of transparency means advertisers using Google's broader digital advertising programs may be unaware if their ads appear within Google AI answers, as Google Ads reporting does not segment performance for these placements [2]. For ChatGPT, ads appear when conversational intent is clarified, with placement determined by ad creative, copy, and landing page, rather than keywords [2].

Similarweb states its insights are derived from real user panel conversations, not synthetic prompts [1]. Harel Amir, General Manager and Head of Product for Similarweb Ad Intelligence, noted that this is a "rare moment when a major ad channel is still wide open," suggesting an early advantage for advertisers who can access this data [1]. Jonathan Bar Vardi of Natural Intelligence, an advertiser on ChatGPT, stated that Similarweb's tool provides visibility into competitor spending, appearance, and performance that was previously unavailable [1].

Divergent Measurement Landscape

The 26% figure for ChatGPT ad penetration aligns with Similarweb's own July 2026 Generative AI Landscape report, which cited 26% for US desktop chats in June 2026, up from 14% in May [2]. That report also measured AI Overviews on 43% of US searches [2].

However, other measurements of these surfaces show significant divergence. Adthena, for instance, recorded 0.00% ChatGPT ad frequency in the United Kingdom during June 2026 and zero ChatGPT ad items across all markets in the same month, while measuring AI Overviews on 23% of UK searches and 18% of US searches [2]. Weeks later, Adthena reported 24.7% United States ChatGPT ad frequency and 5.8% for Google AI Mode, figures it has not publicly reconciled with its earlier June report [2]. Similarweb's "nearly 30%" for Google AI Mode applies to ad-eligible queries, a narrower scope than all queries [2].

What to watch

• Monitor how Similarweb's AI Ads dataset evolves with anticipated future releases, which are expected to add advertiser share of voice, ad categories, and conversational intent [1].
• Observe how Google and OpenAI might respond to the demand for greater ad transparency on their AI platforms, given the current lack of public ad libraries [2].
• Track the adoption of AI advertising by major brands and the competitive dynamics that emerge as more advertisers gain visibility into these placements [1].

The launch of Similarweb's AI Ads highlights the growing importance of advertising within conversational AI platforms and the current opacity surrounding these new ad channels. The varying measurement figures from different firms underscore the nascent and complex nature of tracking ad activity in this evolving space.