The domains most cited by AI and the abrupt adjustment of ChatGPT with Reddit and Wikipedia

Semrusha global company specialized in digital marketing and online visibility, has analyzed the behavior of three of the main generative artificial intelligence models, ChatGPT, Google AI Mode y Perplexityto identify which domains they cite most frequently and how those patterns have changed in recent months. The study, based on more than 230,000 prompts and more than 100 million AI quotes over 13 weeks, from July 14 to October 12, 2025, confirms that Reddit y Wikipedia continue to be the sources most mentioned by ChatGPTbut it also reveals a sharp drop in its citations starting in September, accompanied by the rise of media outlets such as PR Newswire, Forbes o Medium.

In September 2025, many SEO professionals detected a sudden drop in the frequency with which ChatGPT cited Reddit and Wikipedia, traditionally two of its main sources. The change coincided with Google’s decision to remove the search parameter num=100which led part of the sector to relate both phenomena.

However, Semrush’s analysis suggests that this explanation is incomplete. According to data from Semrush’s Organic Research tool, of the approximately 263 million keywords for which Reddit ranks on Google, only about 90 million, 34%, are between positions 21 and 100. That is, reliance on deeper results alone would not justify such a sharp drop in ChatGPT citations.

Reddit and Wikipedia continue to dominate, but with less distance

At the beginning of August, ChatGPT cited Reddit in almost 60% of the responses analyzed. Within weeks, that presence fell to around 10%. Wikipediafor its part, went from appearing in approximately 55% of the responses to less than 20%. After the adjustment, both domains are still the most cited by ChatGPT, but in a much more balanced proportion compared to other sources such as Medium, Forbes or LinkedIn.

In Google AI Mode, citations to Wikipedia remain around 2–3% of the responses, without major changes during the analyzed period. The most cited sources in AI Mode include LinkedIn, YouTube, Reddit and domains owned by Google or strategic allies, such as Google y Google Blogreflecting a more balanced and less volatile mix than that of ChatGPT.

Finally, in Perplexity, the most common domains are Reddit, LinkedIn, NIH, Microsoft y Google. Reddit also registers a slight drop in this engine, but much more moderate than in ChatGPT, while Wikipedia, Microsoft and Forbes experience small increases.

4 keys for marketing professionals

The Semrush study shows that visibility in AI is highly volatile and that the changes do not occur uniformly between platforms. What benefits a brand or domain on ChatGPT may not be replicated on Google AI Mode or Perplexity.

For brands, this means they should monitor visibility on AI engines just as they already do on traditional search results pages. Variations in domain citations are a clear sign of which sources AI models consider “trustworthy” to learn and construct their responses, and understanding which sites dominate citations in a specific niche allows you to identify key partners, media and platforms where you can strengthen your brand presence.

Semrush lays out four key steps that all marketers should follow to stay relevant in this new era where AI and SEO converge to boost visibility:

1. Identify the most cited domains in your sector: Analyze which websites, media and platforms appear most frequently in AI responses related to your category.
2. Assess the current position of your brand: It measures whether the brand is cited, in what contexts and through what reference domains.
3. Design an authority and relationship strategy: Prioritize collaborations, content and public relations with domains that already “weigh” in the AI ​​conversation to reinforce your own brand authority.
4. Combines data from search engines and AI: Use reliable tools to cross visibility in traditional search engines with presence in AI engines and thus have a more complete vision of your digital positioning.