One question comes up again and again when I talk to business owners about AI search: “Where does ChatGPT actually get its search results from?” Some people are sure it is just Bing with a chat window on top. Others have read that it copies Google. A few believe it has its own giant index, like Google does.
The honest answer is that it is a mix, and the mix matters. If you know which indexes ChatGPT can pull from, you know which doors you need to keep open for it. If one of those doors is shut, you can do great SEO work and still never show up in a ChatGPT answer.
In this guide, let me explain in plain words what is publicly known about ChatGPT’s sources, what is only reported or guessed, and why its citations still look so different from Google’s top ten. Then I will give you a simple checklist to make sure every route into ChatGPT is open for your site, and a way to test it yourself.
Why it matters which index ChatGPT searches
An index is simply a big stored list of web pages that a search system has already visited and saved. When someone asks ChatGPT a question that needs fresh information, it doesn’t read the whole internet in that moment. It looks up candidate pages from one or more indexes, reads some of them, and then writes an answer with citations.
So the index is the first filter. If your page is not in any index ChatGPT uses, it can’t be cited, no matter how good it is. This is why I treat “which index” as a technical SEO question first and a content question second.
It also explains a lot of confusion I see in reports. A business ranks well on Google, checks ChatGPT, and finds a competitor cited instead. The usual reaction is “ChatGPT must be broken.” More often, the two systems are simply looking at different lists of pages, then ranking them in different ways.
The stakes are not small. ChatGPT is a big product now. According to TechCrunch on February 27, 2026, OpenAI said ChatGPT had reached 900 million weekly active users, up from 800 million in October 2025. For a wider set of numbers on AI search usage, see my roundup of AI SEO statistics.
Does ChatGPT use Bing to find pages?
Yes, Bing is part of the picture, and this is the best-documented piece. When OpenAI launched ChatGPT search in late 2024, its announcement talked about using third-party search providers. Reporting at the time filled in the name.
InfoQ’s coverage on November 5, 2024 summed up the launch this way: internet searches are performed by third-party engines, including Bing. The same piece notes that OpenAI also partnered directly with selected publishers for content like news and weather. On the same day, the Taiwanese tech site TechBang reported that an OpenAI engineer had confirmed the Bing connection on Reddit, and that OpenAI also gathers data through its own crawling.
In brief, the Bing link is real. But notice the words “including Bing.” Bing was never described as the only source. That small phrase is where a lot of the later debate starts.
What the Bing connection means for you in practice
If ChatGPT can use Bing results, then being properly indexed in Bing is a basic requirement, not a nice extra. Many small business sites have never opened Bing Webmaster Tools. Some have pages Bing has never crawled, or old redirects Bing still holds onto.
I cover the setup in detail in my guide to Bing Webmaster Tools. The same work also helps you in Microsoft Copilot, which leans on Bing even more heavily. I explain that side in SEO for Microsoft Copilot and Bing.
What the reports about ChatGPT using Google results actually say
This is the part that gets exaggerated most, so let me separate what was reported from what is proven.
In August 2025, The Information reported that OpenAI had used a Google scraping service. Search Engine Land covered the report on August 26, 2025, and named the service as SerpApi, a company that collects Google results and sells them through an API. According to that coverage, SerpApi listed OpenAI as a customer as recently as May 2024, a listing that was later removed.
“OpenAI quietly used (and may still be using) a Google Search scraping service to power ChatGPT’s answers on real-time topics”
— Search Engine Land, Report: OpenAI used Google search results via SerpApi
Search Engine Land also pointed out that this sits awkwardly with OpenAI’s public position, which is that ChatGPT search relies on its own crawler, Microsoft Bing and licensed publisher data.
The story kept going. Google took action against SerpApi in December 2025, saying its tool was circumventing security measures that protect Google’s results. Computerworld reported on February 24, 2026 that SerpApi had filed a motion to dismiss and was fighting back.
How I read the Google evidence
- Reported, not confirmed by OpenAI: the SerpApi link comes from journalists and an archived customer page, not from OpenAI documentation.
- Possibly temporary: Google’s legal action makes heavy scraping riskier and harder, so whatever share of results came from Google may have changed since 2025.
- Not the whole story: even if ChatGPT sees Google results, its citations don’t follow them closely, as you will see below.
So my advice is simple. Don’t build your plan on the idea that “ChatGPT is just Google.” Treat Google results as one possible input, not the engine underneath.
OAI-SearchBot: OpenAI’s own crawler for ChatGPT search
The third source is the one you control most directly. OpenAI runs its own crawler for search, called OAI-SearchBot. A crawler is a program that visits pages and saves them, so they can be found later.
“OAI-SearchBot is used to surface websites in search results in ChatGPT's search features.”
— OpenAI, Overview of OpenAI Crawlers
OpenAI’s crawler page lists three different user agents, and each one does a different job. Mixing them up is one of the most common errors I find in robots.txt files.
| User agent | What it is for | What happens if you block it |
|---|---|---|
| OAI-SearchBot | Finding and saving pages for ChatGPT search answers | Your pages won’t appear in ChatGPT search answers (OpenAI says they may still show as navigational links) |
| GPTBot | Collecting content that may be used to train OpenAI’s models | Your content is signalled as off-limits for training. Search inclusion is controlled separately |
| ChatGPT-User | Visiting a page when a user’s request needs it, for example in Custom GPTs or actions | OpenAI says robots.txt rules may not apply, because a person started the visit. It doesn’t decide search inclusion |
Two details from OpenAI’s documentation are worth remembering:
- You can allow OAI-SearchBot and block GPTBot at the same time. Blocking training does not remove you from search.
- OpenAI says changes to your robots.txt for OAI-SearchBot can take about 24 hours to show up in search results.
OpenAI also publishes IP address lists for each bot. That matters if your firewall or CDN blocks bots by default, which is more common than most owners think. I go through the full list of AI user agents in my guide to AI crawlers and how to manage them.
Why ChatGPT’s sources still don’t match Google’s top ten
Here is the interesting part. Even if ChatGPT can see Google results, its citations look very different from Google’s rankings. Ahrefs has run three studies on this, and they all point the same way.
| Ahrefs study (date) | What was tested | ChatGPT overlap with Google top 10 |
|---|---|---|
| AI search overlap (Aug 11, 2025) | 15,000 long-tail prompts | About 8% of in-text citations |
| Is ChatGPT really powered by Google? (Aug 20, 2025) | 118,931 fan-out queries | 6.82%; 83.39% of URLs not in Google’s results at all |
| ChatGPT may scrape Google, but the results don’t match (Sep 3, 2025) | 3,311 short-tail head terms | 10.00% of URLs; 31.80% of domains |
For comparison, the same Sept 2025 study found Perplexity’s short-tail citations matched Google’s top 10 URLs 65.07% of the time. So Perplexity behaves much more like Google. ChatGPT does not. The long-tail study also checked Bing, and ChatGPT’s top 10 overlap there was only about 8.1%. In other words, ChatGPT doesn’t simply copy Bing either.
“ChatGPT (and similar systems) don't just lift URLs directly from Google, Bing, or other indexes.”
— Louise Linehan, Ahrefs, ChatGPT May Scrape Google, but the Results Don’t Match
Four reasons the lists differ
- ChatGPT rewrites your question. It turns one prompt into one or more shorter searches, called fan-out queries. Ahrefs found it averaged 1.78 searches per prompt. Those searches are not the words the user typed, so the results are different too. I explain this in my post on ChatGPT query fan-out.
- It blends sources, then re-ranks. Ahrefs’ working theory is a hybrid: results from Google, Bing, OpenAI’s own index and other search APIs are combined, then ChatGPT picks its own favorites. That theory is not confirmed, so I treat it as direction, not hard science.
- It trusts domains more than pages. ChatGPT cited ranking domains about three times more often than ranking URLs. It may know your site is relevant but pick a different page from it than Google does.
- It picks pages that answer cleanly. A page can rank on Google because of links and history, but ChatGPT needs a passage it can quote. Pages with a clear, direct answer have an edge.
If you want to see how differently each AI tool picks sources, my comparison of source overlap across AI platforms goes deeper.
A simple map of the routes into ChatGPT
Putting it all together, here is how I explain it to clients. There are four routes a page can take into a ChatGPT answer. You don’t need to know exactly how OpenAI weights each one. You just need to make sure none of them is blocked.
| Route | How sure are we? | What you control | How to check it |
|---|---|---|---|
| Bing’s index | Confirmed in launch coverage | Bing crawling, indexing and sitemaps | Bing Webmaster Tools URL inspection |
| Google results (via third parties) | Reported, disputed, may have changed | Normal Google SEO | Google Search Console |
| OpenAI’s own crawl (OAI-SearchBot) | Documented by OpenAI | robots.txt, firewall, CDN bot rules | Server logs, robots.txt test |
| Licensed publisher feeds | Confirmed for selected partners | Not much, unless you are a large publisher | Not applicable for most businesses |
How to make sure your site is visible to each index
Here is how I would do it, in order. Most of this takes an afternoon for a small site.
- Check Google indexing first. Open the Page indexing report in Google Search Console. Make sure your key service and product pages are indexed. If they aren’t in Google, they are unlikely to be anywhere else.
- Verify the site in Bing Webmaster Tools. You can import from Search Console in a few clicks. Submit your XML sitemap and inspect your five most important URLs.
- Turn on IndexNow if your platform supports it. IndexNow is a simple way to tell Bing and other engines when a page changes. My IndexNow guide shows how.
- Read your robots.txt line by line. Look for any
Disallowthat applies toOAI-SearchBotor toUser-agent: *. A blanket block meant for “AI scrapers” often catches the search bot too. - Check your firewall and CDN. Services like Cloudflare can block AI bots with one toggle. Make sure the setting matches your choice in robots.txt. If you want search but not training, allow OAI-SearchBot and block GPTBot.
- Confirm the content is in the HTML. If your main text only appears after JavaScript runs, some crawlers may see an empty page. View the page source and search for a sentence from your main content.
- Look for snippet limits. A
nosnippettag or a very lowmax-snippetvalue limits how much text search systems can show from your page. - Wait, then test. Give robots.txt changes at least a day, based on OpenAI’s 24-hour guidance, then run the test in the next section.
Testing what ChatGPT can actually find on your site
You don’t need special tools to run a basic check. You need a list of questions and a spreadsheet.
The 20-prompt check
- Write 10 questions a customer might ask where your page is a perfect answer. For a plumber, “How much does it cost to replace a water heater in Austin?”
- Write 10 questions that mention your brand directly, such as “What services does [your brand] offer?”
- Run each one in ChatGPT with search on, in a fresh chat. Note whether your domain is cited, which page is cited, and which competitors appear.
- Repeat the same prompts in Bing and Google and note where you rank.
A worked example (hypothetical numbers)
Let’s say a local accounting firm runs the 20-prompt check. Here is what it might find:
- Branded prompts: cited in 9 out of 10. ChatGPT can clearly find the site.
- Non-branded prompts: cited in 2 out of 10, even though the firm ranks in Google’s top five for 7 of those topics.
- Bing check: the firm’s service pages are missing from Bing for 5 of the 10 topics.
In this example, the problem is not ChatGPT itself. The branded results show the bot can reach the site. The weak link is Bing coverage of the service pages, plus pages that rank on Google but don’t give a clear quotable answer. The fix would be Bing indexing work first, then rewriting the opening paragraph of each service page to answer the question directly.
One more tip. Check your server logs for visits from OAI-SearchBot. If you see none at all over a month, something is probably blocking it. My guide to tracking AI traffic in GA4 shows how to measure the visits that come back from ChatGPT once you are cited.
What changes in your technical SEO checklist
Most of classic technical SEO still applies. What changes is the number of “search engines” you need to keep happy, and the cost of a single wrong setting.
| Area | Old habit | What I suggest now |
|---|---|---|
| Indexing checks | Google Search Console only | Google and Bing, every month |
| robots.txt | Set once, never reviewed | Review each quarter; list AI bots by name with clear allow or block rules |
| Bot protection | Default CDN settings | Match CDN rules to your robots.txt choices |
| Rendering | “Google renders JavaScript, so it’s fine” | Keep key text in the initial HTML for all crawlers |
| Reporting | Rankings and organic clicks | Add AI citations and AI referral visits |
None of this replaces good content. But it makes sure good content gets a chance. For the content side of getting cited, read how to get your brand mentioned in ChatGPT Search, and for the bigger picture, our technical SEO guide.
Questions people ask about ChatGPT’s search index
Is ChatGPT search just Bing?
No. Bing is one confirmed source, but Ahrefs found ChatGPT’s citations overlap with Bing’s top 10 only about 8% of the time on long-tail prompts. ChatGPT blends sources and re-ranks them.
Does ChatGPT use Google’s index?
It was reported in August 2025 that OpenAI used SerpApi, a Google scraping service. OpenAI has not documented this, and Google has since taken legal action against SerpApi. Treat Google results as a possible input, not the main engine.
If I block GPTBot, will I disappear from ChatGPT search?
No. GPTBot is for training. OAI-SearchBot is for search. OpenAI lets you control them separately.
How fast does ChatGPT notice a robots.txt change?
OpenAI says changes for OAI-SearchBot can take about 24 hours to show in search results.
Why does ChatGPT cite a different page from my site than the one that ranks on Google?
Ahrefs found ChatGPT cites ranking domains about three times more often than ranking URLs. It may trust your site but choose the page with the clearest answer to its own rewritten query.
Where I would start with ChatGPT visibility this week
If you only do three things, make them these: verify your site in Bing Webmaster Tools, read your robots.txt and CDN settings for OAI-SearchBot, and run the 20-prompt check. Together they tell you whether ChatGPT can reach you, and where the gap really is.
After that, it is about giving ChatGPT pages worth quoting. If you want to know which kinds of pages it tends to cite, my breakdown of ChatGPT’s most-cited sites is a good next read.
If you would like us to audit your crawl access, Bing coverage and AI visibility together, our SEO team does this every week. Get in touch for a free quote and we will tell you exactly what is blocking you.
Further reading on ChatGPT search index
- AI SEO Statistics: Key Numbers on AI Search and Citations
- Do AI Assistants Favour Big Brands Less Than Google?
- AI-Proof Keywords: Finding Queries AI Answers Can't Fully Satisfy
Sources for this ChatGPT search index guide
- Ahrefs – ChatGPT May Scrape Google, but the Results Don’t Match (Sept 3, 2025)
- Ahrefs – Is ChatGPT Really Powered by Google? 118,931 Fan-Out Queries Analyzed (Aug 20, 2025)
- Ahrefs – Only 12% of AI Cited URLs Rank in Google’s Top 10 (Aug 11, 2025)
- OpenAI – Overview of OpenAI Crawlers
- InfoQ – coverage of the ChatGPT search launch (Nov 5, 2024)
- TechBang – ChatGPT Search uses Microsoft Bing and three crawlers (Nov 5, 2024)
- Search Engine Land – OpenAI used Google search results via SerpApi (Aug 26, 2025)
- Computerworld – SerpApi fights back against Google lawsuit (Feb 24, 2026)
- TechCrunch – ChatGPT reaches 900M weekly active users (Feb 27, 2026)
