What counts as a citation in AI search

If you're tracking AI citations, the first thing to get straight is that the big engines don't agree on what a citation is. (For the bigger picture this fits inside, see our intro to Answer Engine Optimization.)

ChatGPT (web_search)

When ChatGPT browses, it returns a set of sources behind the answer. Some are inline-linked in the response. Others are listed but not linked from any specific sentence. We count both. A source the model read is a source the model considered, even if it didn't get a hyperlink.

Perplexity (Sonar)

Perplexity footnotes its claims to numbered sources. The footnote list is the citation set. We count a source anywhere on that list the same way: being footnoted fifth counts as much as being first.

Gemini (Google Search grounding)

When Gemini grounds an answer in Google Search, it returns the pages it drew on as grounding sources. Those links point to a Google redirect host, not the site itself, usually with the site's domain as the title. So we resolve each one to the real domain before checking whether it's yours. Skip that step and every Gemini source looks like Google.

Google AI Overviews

AI Overviews surface a panel of cited sources next to the generated summary. The panel is what we count. Google occasionally inlines a source mid-answer, but the panel is the canonical citation list.

Why the differences matter

Source lists vary a lot in length. In AuditAE checks run May to September 2026, the median Perplexity answer listed 19 sources, Gemini 9, AI Overviews 6 and ChatGPT 3. Longer lists give a site more chances to appear: the audited site's own domain was in the source list in 22% of Perplexity checks, against 11% for ChatGPT. So if you only check Perplexity, you'll think you're cited more than you are, and if you only check ChatGPT, you'll think you're cited less. Those sites are a mix of customer brands and sample audits, so read the numbers as directional.

The honest measurement is to check each engine, count citations consistently, and report on each engine separately. Averaging across engines hides the story. The shift this measurement enables, and why it matters now, is laid out in AI visibility vs. SEO; the fixes that move a brand from mentioned to cited are in How to improve brand visibility in AI search engines.

Two free tools to see where you stand, no login: the citation check shows whether ChatGPT, Perplexity, Gemini and Google AI Overviews cite you for a real buyer prompt; the AI search audit shows whether those engines can fetch, read and trust your site in the first place.