Which forums and user-written sites does AI cite?

Key findings

1. reddit.com tops the list. It is cited in the answers for 22 of 41 brands, ahead of wikipedia.org (14) and wordpress.com (8).
2. Forums and user-written sites get 1.4% of third-party citations: 716 of 51,159.
3. Google AI Mode relies on them most: 2.7% of its citations, against 0.3% in Perplexity.
4. Each engine has its favourite: reddit.com in ChatGPT, Google AI Overviews and Google AI Mode; wikipedia.org in Perplexity.
5. The five most-cited domains take 88.5% of the group’s citations, spread over 14 domains.
6. By sector, they weigh most in technology and marketing (3.1% of citations) and least in health, clinics and pharmacy (0.1%).

Data from Mencoro, October 6, 2026 to November 2, 2026: 9,721 answers to the buyer questions that 41 brands track in Spain. The brands are not named. Last updated on November 3, 2026.

The ranking

Ranked by reach: the number of brands whose AI answers cite the domain at least once, then by citations. Reach says more than volume, because one busy market can pile citations on its own niche sites.

Download the data (CSV)

By engine

By sector

Sectors with three or more brands in the data.

Why user-written content carries weight

Forums answer the questions a brand’s website avoids: what goes wrong, what people regret buying, which alternative they chose. Engines cite them for exactly that reason, especially on comparison and problem questions.

A brand cannot write its own forum threads, and should not try. It can read them: the threads an engine cites for your questions say what buyers doubt, and those doubts are what your own pages should answer clearly.

What to do with this

1. Read the threads each engine cites for your buyer questions: they list the objections your pages have to answer.
2. Take part where your customers already ask, as yourself, with useful answers. Never post fake reviews: engines and moderators catch them.
3. Keep your Wikipedia entry, if you have one, accurate and sourced.

Methodology

• Data: the answers Mencoro captured over the last 28 days for the tracked questions of 41 brands whose market includes Spain, on ChatGPT (with web search), Google AI Overviews, Google AI Mode and Perplexity. Not every brand tracks every engine, and an engine tracked by fewer than three brands is left out.
• What counts: Forums and Q&A sites (Reddit, Forocoches, Quora, Rankia, Stack Exchange and Spanish forums), plus user-written reference sites: Wikipedia, Wikimedia, wikiHow, Medium and hosted blogs.
• Citations: every source link an engine attached to an answer, rolled up to the registrable domain (es.rs-online.com counts as rs-online.com). Each brand’s own domains are set apart and reported separately.
• Source types: assigned from reviewed lists for the most-cited domains and from rules for the rest (public-sector suffixes, universities); anything unlisted counts as a company website.
• Privacy: the brands are not named, and rankings only list domains cited for three or more brands (two on Perplexity and inside a sector).
• Limits: the questions are commercial questions chosen by each brand, not a random sample of what people ask AI, and the mix of sectors shapes the totals.
• Updates: the report is rebuilt every Tuesday from the latest data. Figures quoted elsewhere may come from an earlier week.

How Mencoro captures each answer is public on how Mencoro works.

How to cite this report

Mencoro, “Which forums and user-written sites does AI cite?”, data updated on November 3, 2026, https://mencoro.com/data-studies/top-forums-and-ugc/. You are welcome to use the figures and charts with a link to this page.

More data studies

• Which social networks does AI cite?
• Which Spanish media does AI cite?