Where each AI assistant gets its answers
Andy Bright
Director of Product and Technology
On this page
- The assistants at a glance
- Google AI Overviews and AI Mode
- Google's Gemini app
- ChatGPT
- Perplexity
- Claude
- Microsoft Copilot
- Apple's Siri
- Other assistants
- How closely AI answers follow search rankings
- Different assistants cite different websites, and it changes quickly
- Ads in AI answers
- Which assistants to check first
- What to do next
- Further reading
The AI assistants all answer questions in a similar way, as the first chapter explains. They search the web, read some pages and write an answer. But they don't search the same collection of pages, they don't show their sources in the same way, and they don't favour the same websites. A business can be recommended by one assistant and missing from another on the same day.
This chapter goes through the main assistants one at a time. It covers where each one looks, what it shows as sources, and what that means for a business like Fernhill Coffee. Letting each company's crawler into your site is a job for whoever looks after your website. Most of it happens in robots.txt, a short file on your website that tells crawlers which pages they may visit, and in any firewall, the security software that decides which visitors your website accepts. The technical SEO guide's table of settings for each AI service lists what to allow.
The assistants at a glance
| Assistant | Where it looks for pages | How it shows sources |
|---|---|---|
| Google AI Overviews and AI Mode | Google's search index | Links beside and below the answer |
| Google Gemini app | Google Search | A Sources button, when the answer has sources |
| ChatGPT | OpenAI's own crawler and search partners | Citations in the answer and a Sources list |
| Perplexity | Perplexity's own index | Numbered sources with every answer |
| Claude | Brave Search and other providers Anthropic lists, plus its own crawlers | Citations when it has searched |
| Microsoft Copilot | Bing's index | A Sources list |
| Apple Siri | Pages collected by Apple's crawler, Applebot | Links to sources, for some answers |
An index here means a search engine's database of web pages, the same idea as in the technical SEO guide. If an assistant searches Google's index, your page has to be in Google's index before that assistant can use it.
Google AI Overviews and AI Mode
AI Overviews are the AI-written summaries that appear at the top of some Google search results. AI Mode is Google's chat-style search, where you can ask follow-up questions. In May 2026 Google announced that it was bringing the two together(opens in a new tab) into "one, seamless AI Search experience", live worldwide on desktop and mobile. At the same event, Google said AI Mode had passed 1 billion monthly users. This chapter still names both, because Google's documentation still does.
Both are built on Google Search. Google says they're "rooted in our core Search ranking and quality systems", and that they fetch pages from Google's own index (AI optimisation guide(opens in a new tab)). Google's page on AI features and your website(opens in a new tab) says a page has to be "indexed and eligible to be shown in Google Search with a snippet" before it can be used. A snippet is the short description Google shows under a search result. There are no other technical requirements, apart from a setting in Google Search Console, Google's free tool that shows site owners how Google sees their site. The setting is switched on unless someone turns it off. The technical SEO guide explains that setting.
Google's AI answers don't only use web pages. Google's AI optimisation guide(opens in a new tab) says "generative AI responses can include product listings, product information, and information about local businesses". Google Merchant Center is where shops upload details of their products. Google Business Profile is the listing that shows a business's address, opening hours and reviews in Google Maps. Google says keeping both up to date can help your products and services appear in AI answers.
For Fernhill, this means ordinary SEO is the main route into Google's AI answers. Its subscription page needs to be indexed and to rank for the searches behind the question. Its product details in Merchant Center need to be accurate. Fernhill sells only online, so it can't have a Business Profile, but a business with a shop or café would need one.
Google's Gemini app
Gemini is Google's AI assistant, used in its own app and website. It's separate from Google Search, although it uses Google Search to look things up. Google's documentation for developers says that grounding with Google Search "connects the Gemini model to real-time web content" (Gemini API documentation(opens in a new tab)). That page is written for programmers who build Gemini into their own products, so it may not describe the Gemini app exactly.
Gemini doesn't always show its sources. Its help page says "not all responses include related links or sources", and when they do, a Sources button appears in or below the answer (Gemini Apps Help(opens in a new tab)).
Because Gemini and Google's AI features can use different models and give different answers, check them separately. Google-Extended, a line you can add to your robots.txt file, controls whether Gemini can use your pages, but doesn't affect AI Overviews or AI Mode. The technical SEO guide's AI search chapter explains it.
ChatGPT
ChatGPT, made by OpenAI, decides for itself when to search. Its help page(opens in a new tab) says it searches "when your question would benefit from current information", and people can also ask it to search. When it searches, it rewrites the question into one or more searches, and "sometimes partners with other search providers". The same page names Microsoft, which runs the Bing search engine, and Shopify among them.
Whether ChatGPT also uses Google's results isn't confirmed. The SEO consultant Lily Ray summarises reports(opens in a new tab) that it does, but notes that OpenAI hasn't confirmed this. The practical advice is the same either way, which is to be well placed in both Google and Bing.
ChatGPT also runs its own search crawler, OAI-SearchBot. OpenAI's help page says that to be eligible, a site should allow OAI-SearchBot in its robots.txt file, and allow the internet addresses OpenAI publishes for it through any firewall. It adds that "placement is not guaranteed". If you don't manage these settings yourself, ask your developer or hosting company.
Many ChatGPT answers involve no search at all, as the first chapter explains.
When someone asks about buying something, ChatGPT can show product results. OpenAI says these "are selected independently by ChatGPT and are not ads" (Shopping with ChatGPT search(opens in a new tab)). The chapter on shopping and apps explains how products get there.
ChatGPT has the most weekly users of any standalone assistant. OpenAI said in October 2026 that more than 1.2 billion people use ChatGPT each week (OpenAI(opens in a new tab)).
Perplexity
Perplexity is an AI search engine that shows numbered sources with every answer. It runs its own crawler and index. Its crawler documentation(opens in a new tab) describes two visitors:
- PerplexityBot, which is "designed to surface and link websites in search results on Perplexity". Perplexity says it isn't used to train AI models.
- Perplexity-User, which visits pages while Perplexity answers a person's question. Because a person asked the question, Perplexity says it "generally ignores robots.txt rules".
Perplexity also publishes the internet addresses its crawlers use, and suggests allowing them through your firewall. Again, this is a job for whoever manages your website's security.
Claude
Claude is Anthropic's assistant. When Claude searches the web, its help page(opens in a new tab) says the answer includes citations to the sources it used.
Anthropic runs two crawlers that matter here, according to its crawler documentation(opens in a new tab). Claude-SearchBot "navigates the web to improve search result quality", and Claude-User fetches pages when people ask Claude questions. Anthropic says blocking either one may reduce how often your site appears in Claude's answers.
Claude's web search uses outside search providers as well as Anthropic's crawlers. Anthropic's list of the companies it works with(opens in a new tab) names Brave Search, along with other providers, for web search, and Claude's help page says image results come from Bing. Anthropic doesn't say how it combines them. If Claude matters to your customers, search for your main topics in Brave Search(opens in a new tab), a search engine run by the company that makes the Brave browser, and see whether your pages come up.
Microsoft Copilot
Copilot is Microsoft's assistant, built into Windows, Edge, Bing and Microsoft 365. It looks things up in Bing's index, according to Bing's webmaster guidelines(opens in a new tab), so a page that isn't in Bing's index can't be used in Copilot's answers.
Microsoft also gives site owners a report, still in preview, of how often its AI answers cite their pages. The AI Performance report in Bing Webmaster Tools, Microsoft's free tool that shows site owners how Bing sees their site, covers "Microsoft Copilot, AI-generated summaries in Bing, and select partner integrations" (Bing Webmaster Blog(opens in a new tab)). The measurement chapter explains how to use it.
For Fernhill, Copilot is a reason to set up Bing Webmaster Tools, check that its important pages are in Bing's index, and tell Bing when pages change. The technical SEO guide's chapter on sitemaps and IndexNow explains how.
Apple's Siri
Apple launched a new version of Siri in September 2026. Apple's announcement(opens in a new tab) says it uses "information from across the web", and that it runs on Apple models "custom-built in collaboration with Google and its Gemini models". It launched in beta, in English first, and isn't yet available in the EU on iPhone. Apple's crawler is called Applebot. Apple's page about it(opens in a new tab) says the pages it collects can be used when Siri answers general questions. Those answers "may include links to sources and websites used to help generate the answer". Apple hasn't said how Siri picks which pages to cite. Applebot and its settings are covered in the technical SEO guide's crawlability chapter.
Other assistants
There are many others, including Meta AI, xAI's Grok, DeepSeek and Mistral's Le Chat. Their makers publish much less about how they find and cite pages. The same basic approach works for all of them. Find out whether the company publishes the name of its crawler, and if it does, make sure you're not blocking it. The technical SEO guide's crawlability chapter lists the main ones. If its maker doesn't say how it searches, ask it the questions your customers ask, and decide from the answers whether it's worth any extra effort.
How closely AI answers follow search rankings
Ranking is the order in which a search engine lists pages for a search. If AI assistants simply used the top few results, AEO would be no different from SEO. Several studies have compared the two. All of them come from companies that sell SEO or AI tracking tools, and each measured things slightly differently, so read them as rough guides.
- In July 2025, Semrush found(opens in a new tab) an 82% overlap between the pages Perplexity cited and Google's top 10 results for the same searches. The figure was 67% for AI Overviews, about 35% for AI Mode, and lowest for ChatGPT.
- Ahrefs found that 76% of the pages cited in AI Overviews ranked in Google's top 10 in July 2025(opens in a new tab). By March 2026(opens in a new tab) the figure was 38%, and 31% of cited pages ranked outside the top 100. Ahrefs changed its method between the two studies, and suggests that query fan-out "may be" one reason the figure fell.
- AirOps published a study of 15,000 ChatGPT prompts in March 2026. It found(opens in a new tab) that 55.8% of the pages ChatGPT cited were in Google's top 20 results, either for the question itself or for one of the searches ChatGPT ran. Of the pages ChatGPT looked at, those in first place on Google were cited 43.2% of the time, 3.5 times as often as pages outside the top 20.
- seoClarity found(opens in a new tab) in October 2025 that 90% of AI Overviews cited at least one page from Google's top 10 results, across 362,000 US searches.
Taken together, ranking well in search still helps a great deal, especially for Google's AI features and Perplexity. But AI answers also cite many pages that don't rank near the top, partly because query fan-out means they search for more than one thing. For Fernhill, a strong position for "coffee subscription UK" helps. So do pages that answer the narrower searches behind the question, such as delivery to Ireland or the cost of a monthly plan.
Different assistants cite different websites, and it changes quickly
Each assistant has its own favourite sources, and they shift from month to month.
- Parse(opens in a new tab), a company that tracks AI answers, looked at the week from 28 September to 4 October 2026. Reddit supplied 4.27% of the links in Google AI Mode's answers, but only 0.25% of those in ChatGPT's.
- In Ahrefs' US data, "about 1 in every 5 ChatGPT answers cited Reddit" in March 2026, but by late September "it was about 1 in 43" (Ahrefs, October 2026(opens in a new tab)). Wikipedia fell from 1 in 7 answers to 1 in 35. Ahrefs says ChatGPT "seems to be prioritizing original sources over sites that summarize them".
Studies of "the most-cited websites" go out of date within months, and different studies of the same assistant often disagree. Each assistant tends to favour certain kinds of source for each kind of question. The measurement chapter shows how to find the websites the assistants cite for your own customers' questions.
Ads in AI answers
Some assistants now show paid advertising alongside or inside their answers.
OpenAI began testing ads in ChatGPT(opens in a new tab) in the US in February 2026, for logged-in adults on its free and lower-cost plans. It added Canada, Australia and New Zealand in April, and by August the UK, Mexico, Brazil, Japan and South Korea. OpenAI shows the ads separately from the answer, and says they don't influence what ChatGPT says.
Google is testing ads inside AI Mode answers. At Google Marketing Live in May 2026 it announced(opens in a new tab) that it was testing ads, labelled "Sponsored", that can appear in the lists of recommendations AI Mode gives, as "Highlighted Answers".
This guide is about the answers that businesses can't pay for. If you advertise, treat AI ads as another advertising channel, measured like any other.
Which assistants to check first
You can't give every assistant the same attention, so start with the ones your customers use.
- Google's AI features reach the most people, because they appear inside Google Search. AI Mode alone passed 1 billion monthly users in 2026. Ordinary SEO is the main way in.
- ChatGPT has the most weekly users of any standalone assistant.
- After those, it depends on your customers. Business software buyers may use Copilot at work. If your customers mention Perplexity or Claude, check those too.
To find out, look at which assistants already send visitors to your site, and ask new customers where they heard about you. The measurement chapter explains both. Fernhill starts with Google's AI features, because they reach the most people, and with ChatGPT and Perplexity, because those are the assistants its analytics show sending visitors.
What to do next
- Check that your important pages are in both Google's and Bing's indexes, using Google Search Console and Bing Webmaster Tools. If you haven't set them up, the technical SEO guide's first chapter links to both.
- Check that the crawlers for ChatGPT, Claude and Perplexity can reach your site. The technical SEO guide's settings table lists what to allow.
- Search for your main topics in Bing and Brave Search as well as Google, and note where your pages appear.
- Pick the three or four assistants your customers are most likely to use, and use them for the checks in the rest of this guide.
Further reading
- AI features and your website(opens in a new tab), Google's page on what AI Overviews and AI Mode need from a site.
- Searching the web with ChatGPT(opens in a new tab), OpenAI's explanation of when and how ChatGPT searches.
- Perplexity crawlers(opens in a new tab), Perplexity's description of its crawlers.
- How ChatGPT does query fan-out(opens in a new tab), Ahrefs' October 2026 study of how ChatGPT searches, based on 66.6 million answers and the 15 million searches behind them.