Glossary

What is a source domain in AI search?

Also known as cited domain, AI source, citation source

Definition

A source domain is a website that AI engines cite when they answer questions in your topic, such as a review site, directory, news site, forum or competitor's site. It shows where engines get their information.

Key points

Source domains are the websites AI engines cite in answers about your topic.
Grouping them by type, such as directories, review sites and news, makes them easier to act on.
A rival is often named more because it appears on the sites engines already cite.

What does it mean in practice?

A wedding photographer tracks questions like who is the best wedding photographer in the Highlands. Across many answers, the same few sites keep being cited. Perhaps a wedding directory, a review site, a Reddit thread and two competitor blogs. Those are the source domains for that topic.

Grouping them by type makes them easier to act on. Axiom GEO classifies cited domains as directories, review sites, listicles, social, the brand's own pages, competitor pages and news. AI citation tracking lists the top ones across all your answers.

Why does it matter for AI search?

Source domains tell you where to spend effort. If AI engines lean on one directory, a complete and accurate listing there may matter more than anything on your own site. If they cite best-of lists, it may be worth asking to be included, or writing a fair comparison page of your own.

They also explain why a competitor is named more often. It is usually because they appear on the sites the engines already trust. Reddit threads show up as sources in many topics, and Reddit insights finds the subreddits AI engines cite in yours.

These terms connect to source domains.

Citation, a single link shown as the source of an answer.
Brand mention, when an answer names your business.
NAP consistency, keeping your details the same on every listing.
Grounding, how engines look up sources before answering.

Common questions

Which sites does ChatGPT cite most?

It depends on the topic and the question. For local services, directories and review sites often appear. For software, comparison articles, forums and vendor sites are common. The only reliable way to know for your topic is to run your own buyer questions and record which domains get cited.

What should I do with a list of source domains?

Start with the ones cited most often. Check whether you are listed on them, whether your details are right and whether rivals are featured instead. Then decide where a listing, an update, a review or outreach is most likely to help.

Reviewed 26 September 2026

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