Where Do ChatGPT, Perplexity, Gemini and Google Get Their Information? (We Tested All Four)
By Minel Gunesoglu, founder of Is My Brand in AI · Original research, June 19, 2026
TL;DR: We asked ChatGPT, Perplexity, Gemini and Google's AI Overview the same buyer questions and logged every source each one cited.
- The four engines barely overlap — any two typically shared zero to one source, and no single source appeared across all four.
- Reddit came closest to universal, the one source that bridged the engines.
- Each engine has its own profile: AI Overview the most mainstream, Perplexity the broadest, ChatGPT big publishers plus niche blogs, Gemini the sparsest.
Most advice about "getting cited by AI" treats the AI as one thing. Optimize your page, earn some mentions, and you will show up in the answers. But "the answers" are not one place. ChatGPT, Perplexity, Gemini and Google's AI Overview each run their own retrieval, and we wanted to know a simple thing: where does each one actually get its information, and when you ask them the same question, do they reach for the same sources?
So we tested it. We took a set of ordinary B2B-SaaS buyer questions — "best CRM for startups," "HubSpot vs Salesforce," "how to reduce customer churn," "cheaper alternatives to HubSpot" — and ran them through all four engines in June 2026, logging every source each one cited. (Full method at the bottom; we ran real prompts and recorded what actually appeared, nothing modeled.)
The short answer: no, they barely overlap. The same question produces four almost entirely different source lists. If you are planning your visibility around "AI," you are planning around four different games.
On this page
One question, four different worlds
Here is the cleanest way to see it. This is the source list each engine cited for the exact same query — "best CRM for startups" — on the same day:
| Engine | Sources it cited |
|---|---|
| Perplexity | crm.org, tech.co, zendesk.com, techradar.com, hubspot.com, digitalocean.com, salesflare.com |
| ChatGPT | techradar.com, tekpon.com, toolcheckr.com, Best CRM Reviews, saasprobe.com, Better Launch, reddit.com |
| Gemini | UpliftGTM, Lightfield, Dalil AI, ZoFlowX |
| Google AI Overview | Podium, plus reddit.com, salesforce.com, techradar.com, zoho.com, monday.com, quickbase.com |
Look at how little they share. The only site that appears in more than one list is techradar.com (in Perplexity, ChatGPT and the AI Overview) — and even that one is missing from Gemini. Not a single source is cited by all four engines. Gemini's four sources overlap with the other three engines exactly zero times. The same buyer, asking the same question, gets recommended pages from four non-overlapping corners of the web.
This was not a fluke of one question. We saw the same pattern across every query we ran on all the engines.
How little they actually overlap
For six questions we ran head-to-head through Perplexity, ChatGPT and Gemini (covering recommendation, comparison, how-to and alternative queries). Here is the overlap between the two engines that cite the most sources — Perplexity and ChatGPT — measured as shared domains on the identical query:
| Question | Shared sources (Perplexity ∩ ChatGPT) |
|---|---|
| best CRM for startups | techradar.com (1) |
| best project management software | none (0) |
| HubSpot vs Salesforce | forbes.com, reddit.com (2) |
| Mailchimp vs Klaviyo | technologyadvice.com (1) |
| how to reduce customer churn | none (0) |
| cheaper alternatives to HubSpot | reddit.com (1) |
Two of six questions had zero shared sources. The rest had one or two. The average was under one shared domain per question, out of seven to ten cited by each side. Bring Gemini into the comparison and the three-way overlap collapses to essentially nothing — on most questions, no domain was cited by all three.
The takeaway is blunt: ranking in one AI engine tells you almost nothing about whether you will be cited in another. They are not reading from a shared shortlist.
Where each engine gets its information
The lists are not just different — they are different in character. After running the set, each engine had a recognizable citation style.
Google's AI Overview is the most mainstream. Its sources are essentially Google's own organic winners, condensed: the big review sites (TechRadar), the established vendors (Salesforce, Zoho, HubSpot, Monday), the well-known listicles (Podium), and Reddit. If a page already ranks on page one of Google, it has a real shot at the AI Overview. Classic SEO still does most of the work here. (We have two deeper studies on this engine alone — the most-cited sources in AI Overviews and who it cites by industry — and Reddit was a top source in both.)
Perplexity casts the widest net. It consistently cited the most sources per answer (often eight to ten) and the broadest mix: review sites, vendor pages, Reddit threads, even YouTube videos. For comparison questions like "Notion vs Asana," it pulled in YouTube three times, including a Japanese-language video. Perplexity is the most transparent engine — and the one with the most doors to get in through.
ChatGPT concentrates on a few big publishers, then a long tail of obscure blogs. When its web search is on, a handful of names recur across almost every answer — TechRadar, Forbes, Reddit — alongside a surprising volume of small, unfamiliar sites (think "StackFYI," "Prodify Flow," "RetentionCheck") that look like SEO-built content. Once it even cited an academic arXiv paper for a churn question. One important quirk: with web search off, ChatGPT often cited no third-party sources at all — it answered from memory and linked only to the vendors' own homepages. That is the default experience for a lot of free users, and it means the only "source" many people see is the brand's own site.
Gemini cites the least, and the most obscure. It returned the fewest sources of any engine — often just one or two, sometimes none — and they were almost entirely small, unrecognized sites you have likely never heard of (UpliftGTM, ZoFlowX, RichClicks). On the "how to reduce customer churn" question, it cited nothing at all and answered purely from its own training. Gemini is the hardest engine to influence and the hardest to predict.
You can line these up on a spectrum, from the most predictable engine to the least:
| Engine | Sources per answer | Source character | What moves it |
|---|---|---|---|
| Google AI Overview | medium | Most mainstream (Google's organic winners) | Classic SEO; rank on page one |
| Perplexity | most (8–10) | Broad: reviews, vendors, Reddit, YouTube | Be everywhere; many entry points |
| ChatGPT | medium (5–7) | A few big publishers + many niche blogs | Earn big-publisher and Reddit mentions |
| Gemini | fewest (0–4) | Most niche/obscure; sometimes none | Hardest; least predictable |
The question type changes the sources, too
There was a second pattern hiding in the data: the type of question changes which kind of source gets cited, and it changes the same way across engines even when the specific domains do not match.
- "Best [category]" questions pulled from review sites and listicles (TechRadar, PCMag, G2, Cloudwards). Reddit and YouTube were mostly absent.
- "X vs Y" comparisons leaned on YouTube and Reddit, plus each vendor's own comparison page. This is where brand-owned pages actually got cited.
- "How to" / strategy questions pulled from company blogs — for "reduce customer churn," Perplexity cited ten SaaS company blogs (Stripe, HubSpot, Recurly, Chargebee) and no Reddit or YouTube at all.
- "Alternatives" and "cheaper than" questions were the most community-driven, surfacing Reddit and even LinkedIn posts alongside competitor listicles.
If you only have budget to earn one kind of placement, this tells you where to spend it for the queries you care about.
The few things that do travel across engines
Almost nothing is universal — but three things came closest, and they are the practical core of a cross-engine strategy.
- Reddit. It was the single most common bridge between engines, showing up in comparison, alternative and "best free" answers across Perplexity, ChatGPT and the AI Overview. If there is one off-site place to be discussed, it is the relevant subreddit. (This matches what we found studying Google's AI Overview on its own, where Reddit was the most-cited site by a wide margin.)
- Your own site — but mostly on comparison queries. For "HubSpot vs Salesforce" and "Mailchimp vs Klaviyo," the engines frequently cited the vendors' own comparison pages. A clear, honest "us vs them" page on your domain is one of the few brand-owned assets AI engines reliably reach for.
- A small set of trusted publishers per engine — TechRadar showed up across three of the four engines; Zapier bridged Perplexity, Gemini and the AI Overview on comparison questions. Getting included in the big roundups still pays off in more than one place.
What this means for your brand
The headline finding has a direct, slightly uncomfortable implication: "get visible in AI" is not a single goal you can complete. You are running four campaigns, not one. Here is how we would prioritize them:
- Stop optimizing for "AI" in the abstract. Pick the engines your buyers actually use and treat them separately. Check where you stand in each — there is no shortcut, and the manual method is free; see how to measure AI search visibility.
- Keep doing real SEO for the AI Overview. It is the one engine that rewards classic ranking. If you are on Google's page one, you are most of the way to the AI Overview.
- Earn third-party validation, not just on-page work. Three of the four engines lean heavily on sites you do not own. A page that only says good things about itself is invisible to them. The mechanics of earning those mentions are in how to get cited by ChatGPT and our broader guide to improving brand visibility in AI search.
- Be present where people argue and compare — Reddit threads, comparison roundups, and an honest comparison page on your own site. Those are the placements that travel across the most engines.
- Accept that Gemini is the hard one. It cites little and cites unpredictably. Do not build your plan around it; treat any Gemini citation as a bonus, not a baseline.
The engines do not agree on who to trust. Until they do, your job is not to win "AI" — it is to be one of the few names that keeps showing up no matter which corner of the web a given engine happens to pull from.
Methodology
We ran ordinary B2B-SaaS buyer questions through four AI engines on 19 June 2026 (US, English) and logged every source each cited in its answer.
- Questions: twelve buyer queries across four intents — recommendation ("best CRM for startups," "best email marketing platform"), comparison ("HubSpot vs Salesforce," "Mailchimp vs Klaviyo"), how-to ("how to reduce customer churn," "how to choose a CRM"), and alternatives ("Salesforce alternatives," "cheaper alternatives to HubSpot").
- Coverage: all twelve questions on Perplexity; a representative six (one to two per intent) on ChatGPT and Gemini; three (one per main intent) on Google's AI Overview. Single run per engine-question pair.
- Setup: Perplexity in default web-search mode; ChatGPT on the free tier with web search enabled (we note separately that with search off it cited no third-party sources); Gemini (Flash model); Google AI Overview as shown in standard search results.
- What we recorded: the domains/sources each engine displayed as citations or in its sources panel, in order. AI answers vary between runs, so treat these as a snapshot, not a fixed ranking. We report only what we observed — no figures are estimated or modeled.
This is a deliberately small, hand-run study; the value is in the side-by-side comparison, not the sample size. We will expand it (more runs, more questions per engine) in future updates.