We asked ChatGPT, Gemini and Perplexity the same six questions a buyer would ask about subscription billing software, and three names tied for the lead: Chargebee, Recurly and Stripe Billing were each named in 4 of 6 answers. Maxio followed at 3 of 6, then Paddle, Stax Bill and Vindicia at 2 apiece. No product was named in all six, so the assistants never settled on a single default, and out of 24 products in all, another 17 were named just once. One question, "subscription billing software recommendations", returned no product names at all.
The shortlist flipped completely when we asked for free tools
The sharpest split came on "best free subscription billing software". That one question returned its own roster with zero overlap with the paid picks: Wave, PayPal Invoicing, Invoice Ninja, Zoho Invoice, Square Point of Sale, Odoo, Abby and Avaza. Each of those eight got its single mention there and nowhere else, and not one of Chargebee, Recurly or Stripe Billing appeared. The assistants treated "free" as a separate category rather than a cheaper tier of the same tools, so a vendor with both a free and a paid plan would not carry from one list to the other.
The other four questions barely moved the paid-side shortlist, because they drew on overlapping sources rather than fresh ones. solidgate.com fed "best subscription billing software for small teams", "what subscription billing software should I use" and the empty "recommendations" answer, while younium.com fed those first two plus "most affordable subscription billing software". The same handful of pages was reused across questions that ask quite different things, which is why "best", "small teams", "affordable" and "what should I use" returned roughly the same top names.
The query "subscription billing software recommendations" was the real outlier: it produced no product names from any of the three assistants, even though it pulled seven sources (reddit.com, zoneandco.com, gartner.com, solidgate.com, g2.com, younium.com and appvizer.com). The pages were there, but none pinned down a recommendation the models would repeat. That blank is an opening for whoever publishes the page that answers that exact phrasing.
Zuora shows how thin the long tail is. It surfaced twice, once as "Zuora" and once as "Zuora Billing", which we kept as two separate rows because that is how the assistants wrote it, and each spelling was named just once, in different questions, with "Zuora" appearing on "what subscription billing software should I use". A category-defining enterprise name landed no higher than a one-off, and Zoho fared the same, splitting into Zoho Billing, Zoho Invoice and Zoho Subscriptions at one mention each.
A handful of domains set the whole menu
Every answer was built at least partly on the same short list of pages, and that list, not market share, decided who got named. reddit.com fed all six answers, g2.com and zoneandco.com each fed five, and recurly.com fed four. Those four domains covered the entire top tier. Reddit and G2 are the obvious ones, but zoneandco.com is a NetSuite billing partner's content site, not a review platform or a forum, and it still fed five of six answers. A single high-authority domain in the retrieval index can shape the output even when it is not somewhere buyers would normally look.
Community and review sites showed up but did not dominate: quora.com fed two answers and capterra.com one, against Reddit's six and G2's five, with gartner.com in three. The rest of the 19 source domains lean on vendor and partner pages, and solidgate.com and younium.com each fed three answers despite being billing or payments vendors rather than neutral reviewers.
The vendor-own-domain pattern is the clearest signal in the set. recurly.com fed four answers and Recurly was named in exactly four, the tightest alignment here. We cannot prove the assistants lifted the recommendation straight off recurly.com, but no other vendor matched it: Chargebee and Stripe Billing reached the same four mentions with none of their own domains appearing as a source, so they owe those mentions entirely to Reddit threads, G2 grids and third-party posts. A domain can also feed answers without converting, younium.com fed three but Younium was named just once.
The long tail confirms the mechanism. Salesforce Revenue Cloud was named once and salesforce.com fed only that single answer, while Zuora got its mention with no zuora.com anywhere in the source list, so the assistant most likely picked the name up inside someone else's article. zoho.com appeared only in the free-software sources, so Zoho's mentions on the other questions had no Zoho-owned page behind them either.
What this measurement cannot show is what those pages actually said. A product appearing on a cited page does not mean the page recommended it, only that the name was present, and we cannot see how each assistant weighted a Reddit comment against a vendor blog. The list is the intersection of what the search layer fetched and what the models chose to repeat.
What it takes to get named
None of the three assistants named a product that was not already on one of the pages they read, so getting named is a matter of appearing on those pages, not of market share or feature depth. For a product that was absent, the fix is specific: query each of the six questions, see which Reddit threads and G2 pages rank, and check whether your name is in them. On Reddit that means real participation in the threads that surface for the category. On G2 it means enough verified reviews to land in the subscription billing grid.
The comparison posts matter just as much, because a partner site like zoneandco.com fed five of six answers even though there is no product called Zone, which means it passed mentions to the products its articles cover. If you offer a free tier, a different set of pages decides that answer again: zapier.com, invoiceninja.com, invoicely.com, capterra.com and zoho.com all fed the free question and nowhere else, so the paid-software pages will not carry you into it. Recurly is the one vendor that got its own domain into the mix, by publishing pages that directly answered the buyer questions and ranked well enough to be fetched.
The full list, counted
Every product ChatGPT, Gemini and Perplexity named across the six answers, with how many of the six named it. Share is out of the six answers we read, not the whole category.
| Product | Named in | Share |
|---|---|---|
| Chargebee | 4 of 6 | 67% |
| Recurly | 4 of 6 | 67% |
| Stripe Billing | 4 of 6 | 67% |
| Maxio | 3 of 6 | 50% |
| Paddle | 2 of 6 | 33% |
| Stax Bill | 2 of 6 | 33% |
| Vindicia | 2 of 6 | 33% |
| Abby | 1 of 6 | 17% |
| Avaza | 1 of 6 | 17% |
| Growpay | 1 of 6 | 17% |
Glotier does not sell subscription billing software, so it is correctly absent from these answers, and we would never claim it was named. This measurement is exactly what we run for your own category: the same six buyer questions across ChatGPT, Gemini and Perplexity, with the source page behind every mention. The check is free, no account, and takes about a minute.