--- title: "AI Search Source Overlap: ChatGPT and Google Share 8.4%" url: https://www.suffdigital.com/resources/data-studies/ai-engines-source-overlap description: "AI search source overlap: ChatGPT and Google AI Overviews share only 8.4% of the sites they cite for a question, and any two engines 15.4%. See the data." lang: en --- Share Share on X: https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.suffdigital.com%2Fresources%2Fdata-studies%2Fai-engines-source-overlap&text=ChatGPT%20and%20Google%27s%20AI%20Overviews%20Share%20Only%208.4%25%20of%20the%20Websites%20They%20Cite Share on Facebook: https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.suffdigital.com%2Fresources%2Fdata-studies%2Fai-engines-source-overlap Share on LinkedIn: https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.suffdigital.com%2Fresources%2Fdata-studies%2Fai-engines-source-overlap Share on Reddit: https://www.reddit.com/submit?url=https%3A%2F%2Fwww.suffdigital.com%2Fresources%2Fdata-studies%2Fai-engines-source-overlap&title=ChatGPT%20and%20Google%27s%20AI%20Overviews%20Share%20Only%208.4%25%20of%20the%20Websites%20They%20Cite When ChatGPT and Google AI Overviews answer the same question, only **8.4%** of the websites they cite are the same. Across five AI engines, any two share 15.4% of their sources on average, so being cited by one engine says little about the others. Analysis of 27,665 paired AI answers to 2,984 questions · answers from ChatGPT, Gemini, Perplexity and Google's AI features, September 2026 ## Key Findings 1. 1. ChatGPT and Google AI Overviews share **8.4%** of the websites they cite when answering the same question. Copy stat 2. 2. Any two AI engines answering the same question share **15.4%** of the websites they cite on average, about one in seven. Copy stat 3. 3. ChatGPT shares at most **10.6%** of its cited websites with any other AI engine, and 8.2% with Perplexity, the lowest overlap of any pair. Copy stat 4. 4. Google AI Mode and Google AI Overviews share **37.8%** of the websites they cite, the most of any pair of AI engines. Copy stat 5. 5. The website all five AI engines most often cite for the same question is **irs.gov**, on 14 of 715 questions. Copy stat ## Summary A marketing manager checks Google and is pleased: the company's guide is one of the sources in the AI Overview for its main product question. She asks ChatGPT the same question and the guide is nowhere in the answer. None of the other sources match either. The two engines answered the same question from two different sets of websites. That matters because customers do not all use the same AI tool. A brand that measures its AI visibility in one engine, or pools every engine into one number, can think it is covered when it is invisible to a large share of the people asking. The overlap is small. ChatGPT and Google AI Overviews share only **8.4%** of the websites they cite for the same question. Across all ten pairs of five engines, the average is 15.4%, about one site in seven. Even Google's two AI products, which draw on the same search index, share 37.8%, fewer than four in ten. ## What we measured On September 23, 2026 we asked the same 2,984 everyday questions to five AI engines from a US location: ChatGPT, Gemini, Perplexity, Google AI Mode and Google AI Overviews (the AI summary above Google's search results). For every question and every pair of engines, we listed the websites each engine cited and measured how many they had in common. We kept the 27,665 pairs where both engines cited at least one website, then averaged the results for each pair and for all pairs together. Overlap is the share of websites two engines have in common: the websites both engines cited, divided by all the websites either one cited. An overlap of 100% would mean identical source lists; 0% means no website in common. Websites are counted at the site level, so two different pages on irs.gov count as the same website. ## Any two AI engines share 15% of their sources 15.4% of cited websites are shared, on average, by two AI engines answering the same question. Every engine builds its answers from its own set of sources. The most similar pair is Google AI Mode and Google AI Overviews at 37.8%, the only pair above one in five. Gemini's overlap with Google's two AI products comes next, at 18.2% with AI Overviews and 17.3% with AI Mode, and Perplexity shares about one in six sites with Google's AI features. Websites in common by engine pair Google AI Mode and Google AI Overviews 37.8% Gemini and Google AI Overviews 18.2% Gemini and Google AI Mode 17.3% Google AI Overviews and Perplexity 16.8% Google AI Mode and Perplexity 16.4% ChatGPT and Google AI Mode 10.6% Gemini and Perplexity 10.5% ChatGPT and Gemini 8.6% ChatGPT and Google AI Overviews 8.4% ChatGPT and Perplexity 8.2% All 10 pairs 15.4% Source: Suff Digital analysis of 27,665 paired AI answers to 2,984 questions · answers from ChatGPT, Gemini, Perplexity and Google's AI features, September 2026 Google's two AI products share the most because both sit on Google's search index, yet they still disagree on six sites in ten. Each engine searches differently, reads different pages and picks different ones to cite, so the same question produces a different source list almost every time. ## ChatGPT shares the fewest sources with every other engine ChatGPT is the outlier. It shares at most 10.6% of its cited websites with any other engine, the figure it reaches with Google AI Mode. With Gemini it shares 8.6%, with Google AI Overviews 8.4% and with Perplexity 8.2%, the lowest overlap of any pair. The four pairs that include ChatGPT make up four of the five lowest overlaps in the study. For a business, this means a strong position in Google's AI results does not carry over to ChatGPT, and the reverse. ChatGPT runs its own searches and leans on a different mix of sources, so it has to be checked, and won, on its own terms. ## When all five agree, it is an official source On 715 questions, all five engines cited at least one website in the same round of answers. Full agreement on a single website was rare: the most common one, irs.gov, was cited by all five on 14 of those 715 questions. Apple followed on 11 questions and Microsoft on 9. Questions by website cited by all five engines irs.gov 14 apple.com 11 microsoft.com 9 wikipedia.org 6 nih.gov 4 progressive.com 4 aboutamazon.com 4 bia.gov 3 petmd.com 3 delta.com 3 The websites every engine agrees on are primary sources: the IRS for tax rules, Apple and Microsoft for questions about their own products, the National Institutes of Health for health questions, Delta for air travel. When all five engines do agree, they agree on the definitive source. Everywhere else, each engine goes its own way. ## What this means for marketers Measure each engine separately. A citation report that pools all AI engines hides the fact that each one draws from a different set of websites. Showing up in Google AI Overviews makes it more likely you show up in AI Mode, but tells you almost nothing about ChatGPT. Check the questions that matter to your business in ChatGPT, Gemini, Perplexity and Google's AI features, and track each result on its own. Then aim to be the primary source. The websites every engine agrees on are the official, definitive pages on their subject. Make your site the clearest source on questions about your own products, services, prices and data, with the answer stated plainly, and each engine has a reason to cite you. An ai seo company (https://www.suffdigital.com/seo/ai-seo-services) that tracks all five engines separately, as Suff Digital does, shows where you are missing and why. ## Embed this research Paste this on your site to embed the charts. It links back to the source automatically.

Source: ChatGPT and Google's AI Overviews Share Only 8.4% of the Websites They Cite - Suff Digital

## Cite this study APA Suff Digital. (2026). ChatGPT and Google's AI Overviews Share Only 8.4% of the Websites They Cite. https://www.suffdigital.com/resources/data-studies/ai-engines-source-overlap Plain link ChatGPT and Google's AI Overviews Share Only 8.4% of the Websites They Cite - Suff Digital - https://www.suffdigital.com/resources/data-studies/ai-engines-source-overlap ## Frequently asked questions ### Do ChatGPT and Google cite the same sources? ### How much do AI engines overlap in their sources? ### Which AI engines agree most on sources? ### Which website do all AI engines cite? ## Related studies - AI SEO ChatGPT Cites 3.7 Sources per Answer vs 20 for Perplexity: https://www.suffdigital.com/resources/data-studies/ai-citations-per-answer - AI SEO Google's Gemini Cites No Source in 61.2% of Its Answers vs 2.2% for ChatGPT: https://www.suffdigital.com/resources/data-studies/ai-answers-no-links - AI SEO Google's AI Overviews Cite Reddit 176x More Often Than ChatGPT: https://www.suffdigital.com/resources/data-studies/reddit-citations-ai-answers - AI SEO ChatGPT vs Google: They Agree on the Top Answer Only 20% of the Time: https://www.suffdigital.com/resources/data-studies/chatgpt-vs-google-top-answer ## Structured data ```json [ { "@context": "https://schema.org", "@graph": [ { "@type": "Organization", "@id": "https://www.suffdigital.com/#organization", "name": "Suff Digital", "alternateName": "Suff Digital Marketing", "url": "https://www.suffdigital.com/", "logo": { "@type": "ImageObject", "@id": "https://www.suffdigital.com/#logo", "url": "https://www.suffdigital.com/logo.png", "contentUrl": "https://www.suffdigital.com/logo.png", "caption": "Suff Digital" }, "image": { "@id": "https://www.suffdigital.com/#logo" }, "description": "Suff Digital is a full-stack digital marketing agency that turns websites into predictable revenue engines, SEO, paid media, content, CRO, and web design built around revenue, not vanity metrics.", "slogan": "Digital marketing built for what's next.", "email": "hello@suffdigital.com", "telephone": "+1-629-236-0099", "foundingDate": "2022", "founder": { "@type": "Person", "name": "Matt Suffoletto", "jobTitle": "Founder & CEO" }, "contactPoint": [ { "@type": "ContactPoint", "telephone": "+1-629-236-0099", "email": "hello@suffdigital.com", "contactType": "sales", "areaServed": "US", "availableLanguage": [ "en" ] } ], "address": { "@type": "PostalAddress", "addressLocality": "Nashville", "addressRegion": "TN", "postalCode": "37219", "addressCountry": "US" }, "areaServed": { "@type": "Country", "name": "United States" }, "sameAs": [ "https://www.linkedin.com/company/suff-digital/", "https://www.instagram.com/suffdigital/", "https://www.youtube.com/@suffdigitalmarketing", "https://www.tiktok.com/@suffdigital" ], "knowsAbout": [ "Search Engine Optimization", "Pay-Per-Click Advertising", "Paid Social Advertising", "Conversion Rate Optimization", "Web Design", "Digital PR", "Link Building", "Website Migration", "Website Maintenance and Support", "Technical SEO", "Local SEO", "AI Search Optimization" ], "hasOfferCatalog": { "@type": "OfferCatalog", "name": "Suff Digital Services", "itemListElement": [ { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Search Engine Optimization (SEO)", "url": "https://www.suffdigital.com/" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Pay-Per-Click (PPC) Advertising", "url": "https://www.suffdigital.com/services/ppc" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Paid Social Advertising", "url": "https://www.suffdigital.com/services/paid-social" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Conversion Rate Optimization (CRO)", "url": "https://www.suffdigital.com/services/cro" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Web Design", "url": "https://www.suffdigital.com/services/web-design" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Digital PR & Link Building", "url": "https://www.suffdigital.com/services/digital-pr" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Website Migration", "url": "https://www.suffdigital.com/services/website-migration" } }, { "@type": "Offer", "itemOffered": { "@type": "Service", "name": "Website Maintenance & Support", "url": "https://www.suffdigital.com/services/website-maintenance" } } ] } }, { "@type": "WebSite", "@id": "https://www.suffdigital.com/#website", "url": "https://www.suffdigital.com/", "name": "Suff Digital", "inLanguage": "en-US", "publisher": { "@id": "https://www.suffdigital.com/#organization" } } ] }, { "@context": "https://schema.org", "@graph": [ { "@type": "Article", "@id": "https://www.suffdigital.com/resources/data-studies/ai-engines-source-overlap#article", "headline": "ChatGPT and Google's AI Overviews Share Only 8.4% of the Websites They Cite", "description": "When ChatGPT and Google AI Overviews answer the same question, only 8.4% of the websites they cite are the same. 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Across five AI engines, any two share 15.4% of their sources on average, so being cited by one engine says little about the others.", "url": "https://www.suffdigital.com/resources/data-studies/ai-engines-source-overlap", "creator": { "@id": "https://www.suffdigital.com/#organization" }, "datePublished": "2026-09-24", "dateModified": "2026-09-24", "license": "https://creativecommons.org/licenses/by/4.0/", "isAccessibleForFree": true, "measurementTechnique": "Answers from ChatGPT, Gemini, Perplexity, Google AI Mode and Google AI Overviews" }, { "@type": "FAQPage", "@id": "https://www.suffdigital.com/resources/data-studies/ai-engines-source-overlap#faq", "mainEntity": [ { "@type": "Question", "name": "Do ChatGPT and Google cite the same sources?", "acceptedAnswer": { "@type": "Answer", "text": "Rarely. ChatGPT and Google AI Overviews share 8.4% of the websites they cite for the same question, and ChatGPT and Google AI Mode share 10.6% (September 2026)." } }, { "@type": "Question", "name": "How much do AI engines overlap in their sources?", "acceptedAnswer": { "@type": "Answer", "text": "Two AI engines answering the same question share 15.4% of the websites they cite on average, across ChatGPT, Gemini, Perplexity, Google AI Mode and Google AI Overviews." } }, { "@type": "Question", "name": "Which AI engines agree most on sources?", "acceptedAnswer": { "@type": "Answer", "text": "Google AI Mode and Google AI Overviews, which share 37.8% of the websites they cite for the same question, the highest overlap of any pair of AI engines." } }, { "@type": "Question", "name": "Which website do all AI engines cite?", "acceptedAnswer": { "@type": "Answer", "text": "irs.gov is the website all five AI engines most often cite for the same question, on 14 of 715 questions, followed by apple.com (11) and microsoft.com (9)." } } ] } ] } ] ```