In September 2025, ChatGPT immediately started citing Reddit and Wikipedia—two of its most frequent sources—far much less regularly.
SEOs had been fast to level out a correlation between the decline and a change in how Google serves search outcomes. However is that basically the trigger?
We analyzed immediate information throughout LLMs to see precisely what occurred. However earlier than we get into the analysis, let’s discover what many SEOs suppose occurred and why that may not be the complete story.
The Extensively Mentioned Idea Behind Reddit and Wikipedia Quotation Declines
Google eliminated its num=100 search parameter in mid-September, limiting numerous instruments’ talents to entry URLs past the primary web page of outcomes.
If ChatGPT relied on the num=100 parameter to verify deeper rankings that comprise Reddit and Wikipedia outcomes, this might clarify the sudden drop. One thing Lily Ray, VP of web optimization Technique & Analysis at Amsive, identified on X:
I requested Sergei Rogulin, Semrush’s Head of Natural and AI Visibility, for his ideas.
Personally, I don’t suppose [the num=100 parameter removal] is the foundation trigger. Or at the least, not the one one. Correlation doesn’t all the time suggest causation.
Sergei factors to information from Semrush’s Natural Analysis instrument as help. We are able to see that out of the ~263M key phrases Reddit ranks for in Google, solely about 90M (34%) of these rankings are between positions 21 and 100.
That doesn’t align with how dramatic of a drop we noticed in Reddit citations from ChatGPT, one thing Sergei elaborates on:
I consider the principle purpose for the drop is an try to keep away from over-citing on sure web sites, to be much less biased towards them, whereas producing solutions. Because of this, ChatGPT has develop into extra resilient to manipulation makes an attempt.
What’s clear is that the occasion uncovered how risky AI visibility will be.
Key Takeaways
- Reddit and Linkedin had been among the many high 5 most-cited domains on ChatGPT, Google’s AI Mode, and Perplexity
- ChatGPT had the sharpest adjustment amongst high quotation sources, with important drops for Reddit and Wikipedia occurring in mid-September
- Regardless of the drop in quotation share, Reddit and Wikipedia are nonetheless ChatGPT’s two most-cited domains
- AI Mode has a transparent choice for Google’s owned domains
Examine Methodology
To look nearer at what actually occurred with AI visibility adjustments, we checked weekly citations for greater than 230,000 prompts over 13 weeks throughout three LLMs.
Listed below are the small print:
- We analyzed 230K prompts throughout ChatGPT search, Google AI Mode, Perplexity
- We took weekly snapshots between July 14, 2025 and October 12, 2025 (13 weeks)
- Every week, we studied the highest 25 domains that appeared most frequently amongst AI citations
- We analyzed over 100M complete AI citations
The Most-Cited Domains Throughout AI Platforms
Regardless of the dramatic drop-off in ChatGPT citations, Reddit and Wikipedia are nonetheless among the many high cited domains throughout the LLMs as of October 2025.
Let’s look nearer at a number of the high domains’ quotation volatility throughout the AI platforms we studied.
Reddit: Abrupt Decline on ChatGPT, Extra Secure on AI Mode & Perplexity
ChatGPT cited Reddit in near 60% of immediate responses in early August earlier than collapsing to round 10% by mid-September.
Wikipedia: Abrupt Decline on ChatGPT, Extra Secure on AI Mode & Perplexity
In ChatGPT, Wikipedia dropped from showing in roughly 55% of AI immediate responses to lower than 20%.
In distinction, the portion of LLM responses Wikipedia was cited in on AI Mode and Perplexity stayed constant, holding close to 3% on AI Mode and 0.8% on Perplexity.
This mirrored Reddit’s ChatGPT drop across the similar time and reveals that there wasn’t a systemic drop throughout all LLMs.
LinkedIn: Regular Rise Throughout All Platforms
AI Mode constantly cited LinkedIn in practically 15% of its responses, dipping briefly in early September however rapidly recovering.
ChatGPT and Perplexity cited LinkedIn much less usually, but additionally trended upward after the timing of the Reddit/Wikipedia drop.
It’s potential that LinkedIn content material gained a number of the citations that Reddit and Wikipedia misplaced.
Forbes: Regular Rise Throughout All Platforms
Forbesalso confirmed a transparent progress within the dataset in the identical timeline.
In ChatGPT, Forbes doubled its variety of AI responses with a quotation after September. Forbes’ look in AI Mode and Perplexity confirmed smaller will increase across the similar time.
Winners and Losers After the September Change
Subsequent, we checked out which of the highest websites had the most important constructive or detrimental adjustments in how regularly they had been cited in responses after Google eliminated the num=100 parameter (round September 11, 2025).
The largest winners on ChatGPT? PRnewswire, Forbes, and Medium.
Together with Reddit and Wikipedia, TechRadar skilled a drop in ChatGPT citations.
Probably the most motion on AI Mode got here from user-generated content material (UGC) domains.
YouTube, Reddit, and Fb grew essentially the most, whereas Medium, Quora, and LinkedIn had the most important declines.
The largest constructive adjustments on Perplexity had been for Wikipedia, Microsoft, and Forbes—though these bumps had been minimal in comparison with the volatility on ChatGPT and AI Mode.
The largest total shift on Perplexity was the detrimental pattern for Reddit citations.
The Most-Cited Domains on Particular AI Platforms
We are able to actually see how the Reddit and Wikipedia drop in citations was remoted to ChatGPT with these graphs displaying the motion of the highest 5 most-cited domains on every of the three LLMs.
ChatGPT
Earlier than September, ChatGPT responses cited Wikipedia and Redditabout 5 instances as a lot as the following most-cited domains.
After mid-September, the 2 giants got here nearer to the others, which embody Medium, Forbes, and LinkedIn.
Right here’s a more in-depth have a look at these 5 weeks instantly earlier than and after the removing of the Google parameter in September.
Reddit and Wikipedia dropped dramatically earlier than stabilizing and re-establishing their lead in a extra balanced ratio.
Google AI Mode
AI Mode confirmed a much more balanced mixture of cited domains all through the quarter. Its high cited domains included LinkedIn, YouTube, Reddit, Google, and Google Weblog(all of that are properties that Google both owns or has a significant partnership with).
Whereas there’s some motion—Reddit quotation frequency rises in late August, then falls once more—the general composition on the high stays extra steady than for ChatGPT by the research length.
In contrast with ChatGPT, Google’s AI Mode cites Wikipedia a lot much less regularly. Wikipedia was cited in round 2% of AI Mode responses.
Perplexity
Perplexity’s high sources had been Reddit, LinkedIn, NIH, Microsoft, and Google.
Reddit’s visibility on this platform additionally declined barely in September, however the remainder of the main domains remained comparatively constant.
Why The Latest AI Visibility Adjustments Matter for Entrepreneurs
The information doesn’t inform us precisely why these shifts occurred—however it does present how rapidly AI quotation patterns can change. And that these adjustments aren’t uniform throughout engines.
For entrepreneurs, the takeaway is to begin monitoring these shifts the way in which we already monitor search engine outcomes pages (SERPs).
When quotation patterns shift, it is a sign. These actions inform you which sources AI techniques are studying from and trusting.
What You Ought to Do Now
This high-level information about AI visibility adjustments amongst main platforms is attention-grabbing. However the true alternative is knowing your particular business and subject space.
Which domains dominate AI citations in your area of interest? Which platforms are gaining or shedding floor? The place does your model seem—and the place are the gaps?
Your aim is to take that perception and switch it into motion.
Determine which domains are trusted in your class. Construct relationships with them to strengthen your individual model’s authority.
Semrush allows you to monitor your model’s efficiency on main AI platforms and search engines like google. Plus, you possibly can uncover which domains are shaping conversations in your area of interest to tell future relationships.
Use Semrush to get a glance into what’s occurring from a number of angles.
