What is source authority?
Source authority, in AI search, is the tendency of answers in a category to cite a particular domain. You judge it by seeing the same sites appear across repeated prompts and engines. It is not a universal score, and a famous domain can be irrelevant to your buyers’ questions.
Why it matters for AI visibility
Engines show their preferences through repetition. If three review sites and one community account for most citations on your prompt set, those are the authoritative sources for that set, regardless of how strong their classic domain metrics look in another industry. Source authority matters because outreach and content aimed at unused domains do not change the answers you measured. Build the list from your own logs: domain, URL, which prompts, which engines, and how often. Recompute it when you change the prompt set, because authority is topic-specific. A medical journal is not an authority on warehouse software just because it is trusted elsewhere. Tools can estimate likely sources. Confirm the estimate in live answers before you brief a pitch. When you earn coverage, authority predicts where a citation might come from. It does not guarantee the next answer will pick that page.
Example
Across thirty buyer prompts, two magazine domains and your rival’s docs account for most of the cited URLs. A popular tech blog never appears. For this category, the magazines have the source authority you can act on. The popular blog does not, on this evidence.
Related terms
E-E-A-T is a quality description of a page. Earned media is how you get onto a domain answers already cite. An AI citation is one occurrence that, repeated, is what you use to call a source authoritative.