Co-citation happens when two websites, brands or pages are mentioned or linked together by a third source, even if they never link to each other. If many articles about project management software name your brand alongside two well-known competitors, that repeated pairing is co-citation.
For businesses, co-citation is a way to think about context and company. Being mentioned in the same breath as the leaders in your category can shape how search engines and AI assistants understand what you are and who you compete with, which matters when an assistant is deciding which brands to recommend.
What is co-citation?
Co-citation started in library and information science, long before search engines. In 1973, Henry Small of the Institute for Scientific Information published "Co-citation in the scientific literature" in the Journal of the American Society for Information Science. He defined co-citation as the frequency with which two documents are cited together, and used it to map how scientific papers relate. History of Information notes that Irina Marshakova in Moscow co-discovered the same method.
SEO practitioners later borrowed the idea for the web. In SEO, co-citation usually means two sites or brands being linked or mentioned on the same page by a third party. The idea is that frequent pairing suggests the two are related, even without a direct link between them.
A closely related term is co-occurrence: words and phrases that tend to appear near each other, such as your brand name near "payroll software" or "small business." The two ideas are often discussed together, and the line between them is blurry.
Why co-citation matters
It helps define your category. If your brand keeps appearing next to the same competitors and topics, that context makes it clearer what your business does. This connects to entity SEO, where the goal is for search engines to understand your brand as a distinct thing with clear relationships.
It shapes AI recommendations. Large language models learn associations from the text they're trained on, and AI search tools pull in sources at answer time. A brand that's frequently listed alongside category leaders in reviews, comparisons and roundups is plausibly more likely to come up when someone asks for options. No AI company publishes how this works in detail, so treat it as a reasonable model rather than a confirmed mechanism.
It values mentions, not just links. Co-citation thinking pushes marketers to care about where and with whom they're mentioned, not only about collecting backlinks. That fits a world where brand mentions in trusted sources feed AI answers.
How co-citation works
In citation analysis
In Small's original method, two papers are co-cited when a third paper cites both. The more often that happens, the stronger the relationship. Clusters of co-cited papers reveal the structure of a research field.
In SEO
On the web, the same logic applies to pages and brands. If a buyer's guide links to Site A and Site B, the two sites share context. If dozens of independent guides do the same, the association becomes stronger. Google's guide to its ranking systems says it has systems that understand how pages link to each other to help determine what pages are about. Google hasn't named co-citation as a specific signal, so its exact weight is unknown.
In AI answers
When an assistant answers a question like "best CRM for small teams," it draws on what it learned in training and, for many tools, on sources it retrieves. If the sources it sees regularly list the same group of brands, those brands tend to show up together in the answer. This is one reason prompt testing often reveals the same handful of competitors across tools.
How to build co-citation
- Find where your competitors are listed. Look for roundups, comparison posts, review sites and directories that mention two or more competitors but not you.
- Earn a place on those lists. Pitch editors with useful information, product access or data. Earned inclusion is the goal, not paid placement.
- Be consistent about what you are. Use the same category language on your own site, profiles and pitches so the context around your brand is clear.
- Publish comparison content honestly. Fair "X vs. Y" pages on your own site help clarify where you fit in the market.
- Use digital PR. Coverage in industry publications places your brand alongside the names readers already know. See digital PR.
- Check AI answers. Ask assistants the questions your buyers ask and note which brands appear with yours, or instead of yours.
Common mistakes and misconceptions
"Co-citation is a confirmed Google ranking factor." Google hasn't said so. It confirms that links and how pages link to each other matter, but co-citation as a named signal is an SEO theory.
"Any mention next to a big brand helps." Context matters. Being listed beside competitors in an irrelevant or spammy page is unlikely to help, and paid or manipulative placements can run against Google's spam policies.
"Co-citation and co-occurrence are the same." They overlap, but co-citation is about two entities being referenced by the same source, while co-occurrence is about terms appearing near each other.
"You need a link for it to count." In SEO usage, unlinked mentions can create the same kind of association, especially for AI systems that read text rather than follow links.
Co-citation vs. co-occurrence
Co-citation connects two sources or brands through a third page that references both. Co-occurrence connects words or entities that tend to appear near each other in text. In practice, a strong roundup mention often produces both: your brand is listed with competitors (co-citation) and described with category keywords (co-occurrence).
How Butter approaches co-citation
At Butter, co-citation comes up when we study which brands AI assistants name for a client's key questions. Our monthly AI prompt testing shows which competitors appear and where they're mentioned around the web. That gap analysis tells us which publications, directories and communities to prioritize.
Each month, the GEO plan includes one AI-crawlable content citation and backlink placed on relevant, quality sites, plus off-page recommendations on where a brand should show up next. For brands that want more coverage, our Public Relations add-on focuses on earned media. We don't buy bulk mentions, and we don't promise placement in any AI answer. You can read more on our GEO service page.
Frequently asked questions
What is co-citation in SEO?
Co-citation is when a third-party page mentions or links to two sites or brands together. Repeated pairing suggests the two are related, even if they never link to each other.
Where does the term come from?
It comes from citation analysis. Henry Small introduced co-citation in a 1973 paper, defining it as the frequency with which two documents are cited together. SEO later adapted the idea for websites and brands.
Is co-citation a Google ranking factor?
Google hasn't confirmed it as a named factor. Google says its systems look at how pages link to each other, so the context of links and mentions likely matters, but the exact role is unknown.
Does co-citation affect AI answers?
Likely, though no AI company documents it. Language models learn associations from text, and AI search tools retrieve sources. So brands that are often listed together plausibly get recommended together.