Reddit, by a wide margin. The PR firm 5W published an AI Platform Citation Source Index in May 2026, consolidating six published citation studies into one ranking of the 50 sites that AI platforms pull from most. Reddit sits at roughly 40% citation frequency across every model tracked, well ahead of Wikipedia, YouTube and the news outlets below it. But that single number hides the more useful story, which is that ChatGPT, Claude and Perplexity each read from a different shelf, and the ranking itself does not hold still.
What is the AI Platform Citation Source Index, and what does it actually track?
5W built the index from 680 million individual citations, pulled from six separate published studies covering the period from August 2024 to April 2026, across ChatGPT, Google AI Overviews, Perplexity, Gemini and Claude. 5W's founder, Ronn Torossian, framed the shift bluntly in the announcement: "For 25 years, the most consequential algorithm in communications was Google PageRank. That era is over." Whether or not you accept that PageRank is finished, the underlying point holds. Which sites a model cites most, not which pages rank highest in Google, now decides a meaningful share of what a buyer reads about your company when they ask an AI assistant instead of searching.
Source: 5W's AI Platform Citation Source Index 2026, linked in the article.
Which sites actually dominate AI citations right now?
A small number of domains do most of the work. Reddit's roughly 40% citation frequency makes it the single most-cited source across the five platforms combined, and the top 15 domains in the index capture 68% of all consolidated AI citation share between them. That concentration matters for anyone planning where to spend pitching effort: a handful of sites account for most of what gets surfaced, and the other thousands of sites a brand might chase are fighting over the remaining third.
Two categories outside the obvious news outlets stand out. Journalism as a whole, meaning traditional news publishers, accounts for 27% of all citations across the index, rising to 49% on queries the index classifies as time-sensitive, the kind tied to a recent announcement or event rather than a stable fact. YouTube holds roughly a 200 times citation advantage over the next most-cited video source, and it dominates specifically inside Google AI Overviews, which pull video results more readily than the chat-based assistants do.
Claude's own citation behavior is worth a closer look, since it cites far less often than the other platforms in this index but goes deeper into academic and government sources when it does.
Why does each platform cite different things?
This is where the single "Reddit wins" headline stops being useful on its own. The index breaks citation patterns out by platform, and they diverge sharply.
ChatGPT concentrates on Wikipedia, Reddit, Forbes and Business Insider, with Wikipedia alone making up somewhere between 26% and 48% of ChatGPT's top ten citations depending on the query type, and leans on relatively recent journalism, with 56% of its news citations published within the past twelve months. That share is the reason the Wikipedia question comes up so often now, and also why it is harder to act on than it looks: getting a Wikipedia page for your company depends on independent coverage you did not pay for, which is the one thing you cannot shortcut.
Claude reads differently. It favors The New York Times, The Atlantic and The Economist over the forum and reference sites ChatGPT prefers, and its journalism citations skew noticeably older, with only 36% published in the past year against ChatGPT's 56%. A model built by a company that has talked openly about editorial trust citing more established, slower-moving outlets is a pattern, not a coincidence.
Perplexity leans toward primary sources rather than summaries of them: NIH and PubMed for health and science queries, and B2B authority sites for business and technology queries. That fits how Perplexity positions itself, as a citation-first answer engine rather than a conversational one, something our guide to ranking in Perplexity covers from the crawlability side.
Gemini is the outlier worth a closer look on its own: separate Ahrefs tracking puts Reddit even higher inside Gemini specifically than the consolidated index shows across platforms generally, and Gemini cites far fewer sources per answer than ChatGPT does to begin with. Our dedicated guide to getting cited in Google Gemini covers what that narrower citation count changes about where to earn coverage.
Grok sits outside this index entirely, and its own citation mix leans even further toward social platforms, with Reddit, YouTube and Facebook topping Ahrefs' separate Grok-specific tracking and roughly half its citations tracing back to posts on X itself.
The practical takeaway is that "getting cited by AI" is not one target. A placement that helps with ChatGPT, a Forbes contributor piece or a well-sourced Reddit thread, does comparatively little for Claude, and a PubMed-indexed study does nothing for a platform that does not read it.
How fast does this ranking actually move?
Faster than most brands plan for. The index's own volatility finding is that citation share shifts within weeks, not years, and it gives a specific example: ChatGPT's citation share from Reddit fell from roughly 60% to about 10% within six weeks in late 2025, after what the index attributes to a single parameter change on Google's side, with PR Newswire, Forbes and Medium absorbing most of the share Reddit lost.
That is a different episode from the one we covered in our piece on Reddit's ChatGPT citation collapse in August 2026, where Promptwatch measured Reddit's share of ChatGPT citations falling from a steady 3.8% to 0.52% in four days. The two events are not the same data or the same timeframe, and 5W's index and Promptwatch's report measure citation share differently, which is exactly the point. Two independent trackers have now documented two separate collapses in how heavily ChatGPT leans on Reddit inside a single year. A brand that built its entire AI visibility plan around showing up well on one platform's single favorite source had no cushion either time.
What does this mean for where you should actually try to get covered?
Three things follow from the data, and none of them are "buy ads on Reddit."
Spread earned coverage across source types, not just outlets. Since journalism, reference sites, forums and video each feed different platforms unevenly, a PR plan that only chases traditional press coverage is optimized for Claude and underweighted for ChatGPT and Google AI Overviews. Earned media already accounts for 84% of what AI assistants cite overall, according to Muck Rack's separate study of AI-cited links, so the lever is still earning coverage. The index just argues for earning a wider spread of it.
Treat forum and community presence as part of the mix, not an afterthought. Reddit's citation share is volatile, but even a reduced share still makes it one of the most-cited sources in the index. A brand with zero credible presence in the communities where its category gets discussed is absent from a channel that, on average, still outweighs any single news outlet.
Build toward outlets a platform you care about actually trusts, rather than outlets with the biggest general name recognition. If your buyers lean on Claude for research-heavy questions, a credentialed trade publication read by other reporters is worth more to you than a high-traffic blog Claude rarely cites. Our breakdown of the AI visibility tools that track this kind of citation data covers how to check which platform your own buyers actually use before you commit a pitching budget to one source type over another.
The direct answer, for anyone who read this far
Reddit is the single most-cited source across AI platforms, at roughly 40% citation frequency, and the top 15 domains in 5W's AI Platform Citation Source Index capture 68% of all AI citation share. But ChatGPT, Claude and Perplexity each pull from a different shelf: Wikipedia and Reddit for ChatGPT, established legacy journalism for Claude, primary research and B2B authority sites for Perplexity. The ranking also moves fast, with citation share able to swing by 50 percentage points in a matter of weeks. Plan earned coverage across source types instead of chasing one platform's current favorite, because that favorite has already changed twice in the past year.
If you want help figuring out which sources actually matter for the AI platforms your buyers use, request a quotation and we will walk through what the data says about your category specifically.
