Which Sources Do ChatGPT, Perplexity, and Google AI Actually Cite? We Analysed 24,000 Responses to Find Out

When an AI assistant answers a question, it is drawing on sources. On some platforms, those sources are listed explicitly. On others, they are embedded silently in the response. Either way, the sources an AI cites determine which brands, domains, and voices it treats as authoritative. We extracted every citation from over 24,000 AI responses across ChatGPT, Perplexity, and Google AI Overview, covering 45 UK businesses across sectors ranging from logistics and insurance to investment castings and youth organisations. The dataset covers 8,700 Perplexity responses, 7,000 Google AI Overview responses, and 9,000 ChatGPT responses, each prompted by commercially oriented queries about real markets. The finding that matters most is this: the three platforms cite almost entirely different sources. A brand optimising for one is not optimising for the others. And in most cases, no one is optimising for any of them deliberately. The Only Domain All Three Platforms Agree On Across the entire dataset, only one domain was cited by all three AI platforms: clutch.co. It appeared 140 times in ChatGPT responses, 300 times in Perplexity responses, and 240 times in Google AI Overview responses. Clutch is a verified B2B review and ratings platform. It earns citations on ChatGPT because it has been indexed and linked to extensively over many years. It earns citations on Perplexity because it is a structured, authoritative source of agency data with strong on-page signals. It earns citations on Google AI Overview because it ranks well for commercial comparison queries in organic search. The lesson from Clutch is not that every brand should be on Clutch. It is that the domains which achieve cross-platform citation authority share three properties: they have been publishing structured content for a long time, they are referenced by other authoritative sites, and they give AI systems clear, parseable information to extract. These are not new ideas. They are the fundamentals of publishing, app