Blog · 20 September 2026 · By HeardOf

Who the AI actually cites — and the two engines do not agree

Does ChatGPT or Perplexity cite more sources?

Perplexity, by more than two to one: 391 citations against ChatGPT's 173, from the same 20 buyer prompts on 4 September 2026. Per answer, Perplexity returned 16 to 20 URLs and ChatGPT 5 to 12, in the same run.

Those are the two engines we ran that day, ChatGPT and Perplexity, on the four B2B software categories whose raw answers we still hold — the fifth, dental, was lost to a test run and is left out of every figure below. Twenty prompts, two engines, 40 answers, 564 citations, and 24 measured vendors — the six per category we measured — all counted from the stored answers on 19 September 2026. Nothing estimated.

The count is the least interesting part, because the two engines are not doing the same thing with it. ChatGPT cited 88 distinct domains and Perplexity 204, in the run of 4 September 2026, and the profiles under those numbers are close to opposites:

Will ChatGPT cite my own website?

If you are the vendor being asked about, on 4 September 2026 it did so in 19 of 20 answers, and 44.5% of everything it cited — 77 of its 173 citations — was one of the measured vendors' own pages. Perplexity cited a vendor's own site in 16 of 20 answers in the same run, but usually as one or two links among twenty — 12 of those 16 answers — for 36 of 391 overall, or 9.2%.

The rule behind both figures is the same and worth stating, because it moves ChatGPT's number: a vendor's help centre, knowledge base or CDN counts as the vendor's site. ChatGPT reached for those often — 16 citations across 12 vendor subdomains in the run of 4 September 2026, among them help.productive.io four times, support.scoro.com twice, and kb.bullhorn.com, kb.samsara.com and help.followupboss.com once each — and counting only the bare domain, its share falls to 35.3%. Perplexity's does not move at all under either rule, because it cited no vendor subdomain that day.

The pattern held in every category on 4 September 2026, with the size of the gap varying:

The practical reading is the one we gave on 4 September 2026 and the four-category numbers do not change it: your own pricing, product and help pages are the cheapest source you control, and on ChatGPT they are the source. On Perplexity they are a rounding error, and the citation you would need is written by somebody else. Being named is a separate count from being cited, and in the same run it was the larger one: a brand's name was in the answer text in 45.0% of 240 brand-answer pairs and its own site among the sources in 30.0%, re-counted on 23 September 2026, and the 37 pairs where the name came with no link to the brand's site — 26 of them Perplexity's — are counted brand by brand in named but not cited.

Does Reddit really dominate AI citations?

It is the single most-cited domain, and it is 3.4% of the total: 19 of 564 citations on 4 September 2026 pointed at reddit.com, every one of them from Perplexity, none from ChatGPT. The next three domains — teamwork.com, productive.io and bullhorn.com — are measured vendors' own sites at 13 citations each, in the same run.

We are stating our number because the vendors' own posts on it disagree with each other. Across the five vendor blogs we re-read on 23 September 2026 — Profound, AthenaHQ, Peec, Geoptie and Otterly — six posts carry Reddit in the title or the address and five report a figure from the vendor's own data, pointing different ways: Profound's social-media study heads its conclusion 'Reddit dominates', and one of Otterly's is titled "ChatGPT cut Reddit citations by at least 73% in August 2026". In our run of 4 September 2026 the headline is half right: Reddit was the top domain and it is a Perplexity phenomenon, appearing in 15 of Perplexity's 20 answers and 0 of ChatGPT's. Within Perplexity it is 4.9% of citations, ahead of the next domain at 2.0%, in the same run. That is a lead, not a monopoly.

What Reddit is displacing is also worth knowing. The threads Perplexity cited on 4 September 2026 are the buyer's own question asked in the buyer's own forum — by their thread addresses, r/RecruitmentAgencies on the best ATS for a brand-new agency, r/fleetmanagement on fleet management software recommendations, r/RealEstateTechnology on the best CRM for lead management — and the same thread was cited for more than one prompt in three of the four categories. A buyer who asks Perplexity a "best X for Y" question is being handed a Reddit thread where a different buyer asked it first.

Which websites do ChatGPT and Perplexity cite most?

Vendor sites, one review site, one tech outlet, Reddit, and two domains we had not heard of, 4 September 2026. The top of the table across both engines, 4 September 2026:

Six of the thirteen are measured vendors, and the split column is the story: in the run of 4 September 2026 ChatGPT put 9 of its citations on teamwork.com and 9 on bullhorn.com while Perplexity put 4 on each. techradar.com is a ChatGPT source in the same run, 9 to 2. forbes.com, ustechautomations.com and wifitalents.com are Perplexity sources in the same run, 8 to 0 each. monday.com, which is not one of the 24 brands we measured in any category, was cited 8 times in the same run, 7 of them by Perplexity — a vendor from outside the category answering a question about the category.

The last two domains in the table are not the same case, and one of them is already documented. A study published on 2 September 2026 by Trellner, of Perplexity's sources across 380 software categories, found 59.8% of cited sources outside the top 100,000 sites and 215,128 machine-generated buying guides published across three brands — which the pool cited 181 times, 2.4% of its citations — and wifitalents.com is one of the three brands it names. Our run agrees with the shape: all 8 of wifitalents.com's citations on 4 September 2026 came from Perplexity, and all 8 are pages under its /best/ path — /best/fleet-maintenance-software/, /best/staffing-agencies-software/, /best/client-proofing-software/ among them — the path pattern the study counted. ustechautomations.com is not one of the three brands that study names, and we have not opened it. What our own data shows, in the same run, is 8 citations, all from Perplexity, all under a blog path, with addresses that pair the same two vendors more than once — Bullhorn against JobAdder for staffing agencies and again for recruiting firms, Bullhorn against Vincere for each — and that is a description of the addresses, not a verdict on the pages. Whether it is the same kind of site as the other is a question we did not check.

Do ChatGPT and Perplexity cite the same sources?

Rarely at the page level: 7 of the 463 distinct pages cited in the run of 4 September 2026 were cited by both engines — two teamwork.com pages, bullhorn.com's applicant-tracking-crm page, the productive.io and recruitcrm.io home pages, techradar.com's best-gps-fleet-tracking page and theclose.com's best-real-estate-crm page. A detail the raw strings carry on their own, in the same run: ChatGPT appends its own tracking parameter, utm_source=openai, to 151 of its 173 citations, and Perplexity appends nothing; pages here are counted with the query string removed, as the method section states. At the domain level the overlap on 4 September 2026 is 23 of 269, and 11 of those 23 are measured vendors' own sites; the other 12 are g2.com and learn.g2.com, techradar.com, monday.com, housingwire.com, loxo.co, recruitcrm.io, thedigitalprojectmanager.com, ziflow.com, linxup.com, sierrainteractive.com and theclose.com.

The pool is also thin in a second way: 388 of the 564 citations — 69% — went to a page that no other answer cited, and 165 of the 269 domains appeared exactly once, 61%, all on 4 September 2026. Concentration lives at the domain level, in the vendors and Reddit, and evaporates one level down. A page cited once in 40 answers is, on this evidence, a page the engine found that day rather than one it returns to. Whether those pages also rank in a search engine for the prompt is not something this run measured; the published overlap figures between AI citations and rankings, each with the unit it counted, are compiled in do AI answers cite the pages that rank?.

This is where our run overlaps with the Trellner study and where it does not. Trellner measured one engine, Perplexity, on one day, 2 September 2026, one prompt wording and one run per category with no repeat sampling — its own description — and published the dataset and scripts under CC BY 4.0. Two days later, on 4 September 2026, we measured two engines on one day, 20 prompts, one run each, in four B2B categories. Ours is the only B2B-SaaS replication of that citation-pool finding we know of as of 19 September 2026, and it agrees on the shape: a long tail of once-cited pages under a short head. It adds the thing Trellner could not see with one engine: the head is not the same head. ChatGPT's is the vendors; Perplexity's is Reddit and the outlets. One more thing Trellner measured for one engine is now counted for both, twenty days after the run: against Tranco's list of 23 September 2026, 64 of ChatGPT's 173 citations and 240 of Perplexity's 391 point at a domain outside the top 100,000; and of the 253 of those 269 domains whose robots.txt we could read on 24 September 2026, 7 disallow an OpenAI or Perplexity bot on every path — the per-bot count is in do the sites ChatGPT and Perplexity cite block their crawlers?.

One run per prompt is a photograph, and two published studies say so. Schulte, Bleeker and Kaufmann, on arXiv on 8 April 2026, recommend at least 8 runs per prompt per day when source-level coverage is the question, and Selvam and Ghosh's CITECHOICE, on arXiv on 14 September 2026, found binary citation decisions agreeing 85.0% of the time across 120 regenerated cells — one in seven flips. So the per-URL rows above will not reproduce exactly on a re-run, and we have not re-run them. The contrasts we lead with from 4 September 2026 — 0 against 19, 44.5% against 9.2%, 7 shared pages in 463 — are large enough that we would expect the direction to hold, and that expectation is ours, not a measurement.

So does ChatGPT or Perplexity drive more traffic?

We do not know, and a post that answers this from a citation count is guessing. We recorded which URLs each engine cited on 4 September 2026, not whether anyone clicked them, and as of 19 September 2026 we know of no click report from either engine that a site owner can read for their own pages. Google's Search Console, rolled out globally on 31 August 2026, reports impressions and which of your own pages appeared, by country, for Google's own generative features — not clicks. A click that does happen reaches your site, and how to see ChatGPT and Perplexity visits in your analytics covers where your analytics may show it.

What the count can tell you is narrower and still useful. In our run of 4 September 2026 a ChatGPT citation was one link among a median of 9, and a Perplexity citation one among 20. A vendor's own site was in 19 of ChatGPT's 20 answers that day; it was in 16 of Perplexity's, and in 12 of those 16 it was one or two links of twenty. If your site is going to be clicked from an AI answer, on ChatGPT it will most likely be your own page that is clicked, and on Perplexity it will most likely be a page about you that someone else wrote — a Reddit thread, a roundup, a review profile — with your own page one link in twenty when it is there at all.

That changes what the work is, engine by engine, and the five things to do about it are already written up in how to get your SaaS cited by ChatGPT and Perplexity from the same run; this post is the source-level evidence under that advice, restricted to the categories whose raw answers we still hold. One thing has moved since then: OpenAI announced an advertising platform on 16 September 2026, with Sponsored Agents in test in the US. What it does to ChatGPT's citation pool is a before-and-after measurement we have not run.

How was this measured?

On 4 September 2026 we asked ChatGPT and Perplexity five buyer prompts in each of four B2B software categories — creative agency project management, staffing ATS and recruitment CRM, fleet management and GPS tracking, real estate CRM — and stored every answer with every URL the engine returned as a source: 20 prompts, 40 answers, 564 citations, 463 distinct pages, 269 distinct domains. The 20 prompts are the four non-dental blocks of the 25 published verbatim in the post of 4 September 2026 linked above; the 24 measured brands are the six per category recorded in the stored run, of which that post names three per category. Every figure in this post was re-counted from those stored answers on 19 September 2026.

The counting rules, because they move numbers. A domain is the host with www. removed, so help.fleetio.com and fleetio.com are two domains; collapsing subdomains gives 246 rather than 269 for the run of 4 September 2026. For the vendor-own share, a vendor's subdomain counts as the vendor's site; under the bare-domain rule ChatGPT's 44.5% reads 35.3% and Perplexity's 9.2% is unchanged, in the same run. A page is the host plus the path, with the query string dropped, because ChatGPT tags 151 of its 173 citations in the run of 4 September 2026 with utm_source=openai and Perplexity tags none. A page is counted once per answer that cited it, and no answer cited the same page twice. The study is two engines; the audit we sell asks four, Gemini and Google AI Overviews included, as of 23 September 2026, and an audit's source counts pool every engine that answered, up to four, rather than two.

The run originally covered five categories, and the post of 4 September 2026 reported it that way. On 18 September 2026 a test run overwrote the dental category's stored answers and cited URLs. The figures in that earlier post came from all five categories and are not re-derivable from what we held on 19 September 2026; the figures here come from the four that are, which is why they are smaller and not identical. If you are comparing the two posts, that is the whole explanation, and the measurement date is the answer to any challenge, not a correction.

Everything this post says about our own run — the counts, the shares, the rules, what was lost — comes from our own stored answers as re-read on 19 September 2026, and carries that date or the run date in the sentence that makes it. That is the half of this post a reader cannot check, and we are saying so rather than letting you find the seam. Everything else carries a link or a date you can follow: the Trellner study is at trellner.com, dated 2 September 2026; Schulte, Bleeker and Kaufmann and Selvam and Ghosh are on arXiv, dated 8 April and 14 September 2026; the Search Console report is Google's own announcement; the advertising platform is OpenAI's announcement of 16 September 2026; the six competitor posts are from our own read of five vendor blogs on 19 September 2026. Where we did not check, the text says so.

How to see ChatGPT and Perplexity visits in your analytics