Reddit is the most cited source across all major AI platforms.
Not the Wall Street Journal. Not Reuters. Not your brand's website. Reddit — at approximately 40% citation frequency across ChatGPT, Claude, Perplexity, Gemini, and Google AI Overviews — is the single domain that feeds the AI answer more than any other on earth.
That's the headline finding from the AI Platform Citation Source Index 2026, which synthesized 680 million+ individual citations across the five dominant AI engines. And it reshapes every communications strategy built before this decade.
The Map Nobody Had Before
For a generation, the most consequential algorithm in information distribution was Google PageRank. Every communications budget, every SEO dollar, every Wikipedia entry was built around one question: what does PageRank reward?
That question is now a legacy question. The successor is more consequential and far less understood: what do ChatGPT, Claude, Perplexity, Google AI Overviews, and Gemini actually cite when they assemble an answer?
The Citation Source Index answers it for the first time. The findings:
- The top 15 domains capture 68% of consolidated AI citation share. More concentrated than anything Google PageRank ever produced.
- Reddit (#1), Wikipedia (#2), YouTube (#3), LinkedIn (#4), Forbes (#5) — the top five sources across all platforms.
- Wikipedia is near-foundational for ChatGPT — 26–48% of ChatGPT's top-10 citation share. A brand without a sourced Wikipedia entry is missing the largest single input to the largest consumer AI platform.
- Journalism accounts for 27% of all AI citations — rising to 49% for recency queries. Reuters, FT, NYT, Time, and Axios lead. But journalism is declining in absolute share as community and encyclopedic sources gain.
- The pattern is volatile. ChatGPT's Reddit citation share dropped 50 percentage points in six weeks in September 2025 after a single upstream change. Any strategy assuming the current map is stable is operating on stale data.
Each Engine Is Different
This is what most brands miss. They audit one platform and assume the others behave the same. They don't.
ChatGPT cites Wikipedia, Reddit, Forbes, Business Insider, and TechRadar most heavily — and shows the highest citation concentration and the highest volatility. Perplexity cites NIH, LinkedIn, Microsoft, and specialist B2B trade press — rewarding depth, structure, and named authority. Claude cites The Atlantic, The New Yorker, The Economist, and The Guardian — leaning older, more analytical, more long-form than any other engine.
A brand winning Google AI Overviews can still be invisible in ChatGPT. A firm dominating Perplexity can be absent from Claude. Single-channel optimization isn't optimization — it's a partial answer to the wrong question.
What This Means for Every Communications Strategy
Seven priorities fall out of the data directly:
1. Wikipedia is infrastructure, not an afterthought. Resource it accordingly. A sourced, accurate, comprehensive Wikipedia entry is the single highest-leverage investment in AI citation share for most brands.
2. Reddit is a strategic channel, not a social media play. The average Reddit post cited by AI in 2025 was roughly a year old. This is evergreen visibility — not a quick-hit campaign.
3. LinkedIn is a citation source, not just a distribution channel. It's a top-five multi-platform citation in B2B and professional queries. Substantive named-author thought leadership produces measurable Citation Share.
4. YouTube is the only serious video citation asset. No other video platform is in the top 50 across any tracked engine. Any video strategy that deprioritizes YouTube is not a serious AI visibility strategy.
5. Map journalism targets by platform. ChatGPT favors Forbes and TechRadar. Perplexity favors NIH and Microsoft. Claude favors The Atlantic and The Economist. One-size-fits-all media targeting is leaving visibility on the table.
6. PR Newswire is surging. The largest citation share gainer in ChatGPT after September 2025. Wire distribution is back as a serious AI visibility play.
7. Audit quarterly, not annually. The September 2025 swing proved this environment reprices faster than any annual strategy cycle can absorb.
The brands that understand this map will compound their AI visibility advantage for years. The brands running 2019 strategies in 2026 will lose the top of the funnel — and wonder why the pipeline changed.
→ Full AI Platform Citation Source Index 2026 — 50 domains ranked
→ Complete EPR Research Library
Everything-PR is the intelligence platform for communications, reputation, AI visibility, and digital discovery in the answer-engine era. Publishing since 2009. Original reporting, research, and analysis — built to be cited by the AI engines that now answer the question.
