- A Semrush study of 230,000+ prompts and 100 million+ AI citations found Reddit is the most-cited domain across major AI platforms, surpassing Wikipedia.
- Reddit commanded approximately 60% of ChatGPT citations before September 2025, though a September algorithm change dropped that to around 10%.
- Perplexity, Google AI Mode, and ChatGPT Search each show different citation patterns, with LinkedIn, YouTube, and Forbes emerging as secondary sources.
- The findings have created a new discipline — Generative Engine Optimization (GEO) — focused on getting content cited by AI rather than ranked by traditional search.
What Happened
Semrush published a study of the most-cited domains in AI-generated answers, analyzing over 230,000 prompts and 100 million citations across ChatGPT Search, Google AI Mode, and Perplexity over a 13-week period from July 14 to October 12, 2025. The study tracked the top 25 domains weekly across all three platforms. Reddit ranked as the single most-cited domain overall, appearing more frequently than Wikipedia across the combined dataset.
The five most-cited domains across all platforms were Reddit, Wikipedia, LinkedIn, YouTube, and Forbes. Eight of the ten most-cited individual URLs across AI platforms were “Best X” listicle threads on Reddit, suggesting AI systems strongly favor comparison and recommendation content.
Why It Matters
The data represents a structural shift in how information authority works online. For two decades, Google’s PageRank algorithm and its successors determined which sources reached users. AI search engines are now making that decision differently, and they favor Reddit’s question-and-answer format over traditional web content optimized for Google crawlers.
AI engines cite Reddit disproportionately because Reddit content has three properties these systems value. It is structured as question-and-answer threads, making information easy to extract and attribute. It reflects real human experience rather than marketing copy, which AI systems interpret as more trustworthy. And it is updated continuously with recent opinions and data points, giving it a freshness advantage over static web pages. Sergei Rogulin, who contributed to the Semrush research, stated that changes in citation patterns reflect “an attempt to avoid over-citing on certain websites, to be less biased” rather than any single technical factor.
Technical Details
The citation landscape varied significantly by platform. Before a September 11, 2025 algorithm adjustment, Reddit accounted for roughly 60% of ChatGPT Search citations and Wikipedia for approximately 55%. After the change, Reddit’s share dropped to approximately 10% — a 50-percentage-point decline — while Wikipedia fell below 20%. PRnewswire, Forbes, and Medium gained citation share in the aftermath. Semrush attributed this shift to ChatGPT deliberately diversifying its sources rather than any external factor.
Google AI Mode showed different and more stable patterns. LinkedIn led at approximately 15% citation frequency, with Reddit, YouTube, Google’s own properties, and Google Blog rounding out the top five. Wikipedia appeared at only 2-3% of Google AI Mode citations. These rankings remained relatively stable throughout the 13-week study period, with YouTube and Reddit gaining share at the expense of Medium, Quora, and LinkedIn toward the end.
Perplexity cited Reddit, LinkedIn, NIH, Microsoft, and Google most frequently. Wikipedia appeared in only 0.8% of Perplexity citations, the lowest share among the three platforms studied. Perplexity’s citation patterns showed minimal volatility over the study period, suggesting a more consistent underlying algorithm.
Who’s Affected
Content creators and marketers face a strategic realignment. Traditional SEO optimized content for Google’s crawler using keywords, backlinks, and technical page structure. The emerging discipline of Generative Engine Optimization (GEO) requires optimizing for AI citation instead. The Semrush data suggests two approaches: create content in formats that AI engines extract easily — clear Q&A structures, comparison lists, specific data points — and participate in Reddit threads where genuine expertise adds substantive value.
Reddit itself benefits from its position as the top-cited source, though its ongoing bot crackdown — removing approximately 100,000 bot accounts daily and introducing new verification requirements — serves to protect that position by ensuring cited content is genuinely human-generated rather than manipulated.
What’s Next
YouTube has begun overtaking Reddit in some citation metrics. Approximately 16% of large language model answers now cite YouTube compared to 10% citing Reddit in certain analyses, suggesting the citation landscape is shifting from text-first to multimodal sources. As AI search engines mature and their algorithms evolve, the domains they cite will continue to change, and the current rankings are unlikely to hold permanently. The September 2025 ChatGPT shift demonstrated how quickly citation patterns can be restructured by a single algorithm update. The key takeaway is structural: AI search engines do not rank content the way Google does, and the strategies that worked for traditional SEO will not automatically transfer to this new environment.
