Nessus was the only product named in all 6 of 6 answers when we asked ChatGPT and Gemini which vulnerability scanning software is best. We ran six buyer questions on 2026-08-04, gave the assistants one live web search each, and wrote down every product named and every source domain behind the answer. Nessus is the one name no phrasing could shake loose: best, cheapest, free, or built for small teams, it showed up every single time.
After Nessus, the drop-off is steep. Rapid7 InsightVM came second, named in 4 of 6 answers (67%). Three tools tied for third at 3 of 6 (50%) each: Nmap, OpenVAS, and ZAP. Everything below that landed at 2 of 6 (33%) or a single mention. In total, ChatGPT and Gemini named 24 different product labels across the six answers, but only 5 of them were named in at least half.
How the shortlist changed from one question to the next
The word "affordable" barely changed the list. The bare "best vulnerability scanning software" question returned 8 names, and "most affordable vulnerability scanning software" returned 8 as well, with 6 of the 8 identical: Nessus, OpenVAS, Rapid7 InsightVM, Acunetix, Nmap, and ZAP appeared in both. The only real swap was Tenable dropping out of the "best" answer and Haxore coming into the "affordable" one, a tool that appeared in no other question. If you sell here, "best" and "affordable" are effectively the same query.
The word "free" is where the shortlist actually broke apart. "Best free vulnerability scanning software" returned only 4 names, and just 1 of them, Nessus, carried over from the "best" list. The other three were unique to the free question: Wazuh vulnerability scanner, ZeroThreat, and the Website Vulnerability Scanner from Pentest-Tools.com. None of those three appeared in any of the other 5 answers. The open-source and freemium names only surface when a buyer types the word "free."
"For small teams" pulled in a fresh cast too. That question named 8 tools, and 5 of them showed up nowhere else in the entire run: Qualys VMDR, Wiz, Astra Pentest, Microsoft Defender Vulnerability Management, and Vulscan. Nessus and Rapid7 InsightVM anchored this list like the others, but the buyer-segment phrasing is what surfaced Wiz and Microsoft Defender at all.
Across all six questions, 15 of the 24 product labels were named exactly once. QualysGuard showed up only in "best." A bare Rapid7 and Saner CVEM appeared only in "what should I use." Kiuwan, Qualys Vulnerability Management, and WithSecure Elements Vulnerability Management appeared only in "recommendations." A tool named once is one source page away from never being named at all.
The source map
One domain fed every answer: reddit.com appeared in all 6 of 6 source lists. Behind it, three domains tied at 5 of 6: gartner.com, owasp.org, and safe.security. redcanary.com followed at 4 of 6. So the recommendations were built mostly on a community forum, an analyst site, a standards body, and two security-company roundups, not on vendor ad pages.
Review directories barely registered. g2.com appeared in 2 of 6 answers, on the "small teams" and "most affordable" questions. Capterra did not appear at all, and no other review directory did either. If you are a vulnerability-scanning vendor pouring budget into G2 badges, note that G2 fed a third of these answers while Reddit fed all 6 of 6.
Here is the most useful pattern in the whole run: three vendor domains fed an answer and got their own product named in that same answer. In the "free" question, pentest-tools.com was a source and the Website Vulnerability Scanner from Pentest-Tools.com was named, and zerothreat.ai was a source and ZeroThreat was named. In the "recommendations" question, kiuwan.com was a source and Kiuwan was named. When your own page is in the retrieved set, you tend to be in the answer.
The reverse is visible too. safe.security fed 5 of 6 answers and ox.security fed 2 of 6, yet neither company's own product was named in a single answer. Both were cited as the authors of roundup lists that name other people's tools. Being the source is not the same as being the pick: a listicle you wrote can get retrieved and still hand the recommendation to Nessus.
What to do if you sell vulnerability scanning software
The lesson from this data is narrow and practical: the source list, not your market share, decides whether an assistant names you. Haxore, ZeroThreat, and Vulscan are not household names, and each was named on the strength of one or two pages that happened to be retrieved (1 of 6 each). Nessus wins at 6 of 6 because it sits on nearly every page these assistants read, not because a model consulted a leaderboard.
So the work is to be present in these exact places: the Reddit threads that fed all 6 answers, the Gartner, OWASP, and Red Canary roundups that fed 5, 5, and 4 of the 6, and, as the Kiuwan and ZeroThreat cases show, your own indexable comparison pages. You do not need all 13 source domains we recorded. You need to be on the handful that get pulled for your category's questions.
The full list, counted
| Product | Named in | Share |
|---|---|---|
| Nessus | 6 of 6 | 100% |
| Rapid7 InsightVM | 4 of 6 | 67% |
| Nmap | 3 of 6 | 50% |
| OpenVAS | 3 of 6 | 50% |
| ZAP | 3 of 6 | 50% |
| Acunetix | 2 of 6 | 33% |
| Qualys | 2 of 6 | 33% |
| Snyk | 2 of 6 | 33% |
| Tenable | 2 of 6 | 33% |
Two brands are split across more than one label in this table and in our raw data, and we have left them split on purpose. Qualys appears four separate ways: Qualys (2 of 6), plus QualysGuard, Qualys Vulnerability Management, and Qualys VMDR at 1 of 6 each. Rapid7 appears twice: Rapid7 InsightVM (4 of 6) and a bare Rapid7 (1 of 6). We are not adding these up, because the assistants wrote them as different names, and the count we can stand behind is the one measured for each label. A vendor tracking its own visibility would want to watch every label, since a buyer never sees the sum.
Glotier does not sell vulnerability scanning software, so we are correctly absent from all 6 of these answers, and we would not fake our way in. But this measurement is the whole of what we do: point the same six buyer questions at ChatGPT and Gemini for your category, then show you who got named, in which sub-question, and which source page put them there. If you want your own category's version of this page, the check is free, needs no account, and takes about a minute.