Perplexity cites YouTube, ignores Reddit. GEO advice has a problem.

The best piece of AI search research this month wasn't a survey. It wasn't a thought-leader post. It was one consultant hooking `window.fetch` in his browser and reading what Perplexity actually streams to the page before the answer renders.

Suganthan Mohanadasan published the teardown on Search Engine Journal this morning. He captured eight Perplexity Pro sessions on a single logged-in account, read the raw wire data, and found something the industry has been guessing at for two years: Perplexity does not treat all citation sources equally, and the pattern of what gets retrieved versus what gets cited flips depending on query intent.

The headline finding, buried in the middle of a very long piece: YouTube gets cited heavily. Reddit gets retrieved and ignored.

That single sentence should reshape a decent chunk of the GEO advice being sold to UK businesses right now. Because the received wisdom — the "go do Reddit" playbook that got popular after the ChatGPT teardowns last year — turns out not to transfer between engines. And nobody selling GEO retainers is telling you that.

The Reddit consensus was always thinner than it looked

For most of 2025, the standard GEO advice ran something like this: LLMs cite Reddit heavily because Reddit content is high-context, first-person, and well-indexed in training data. Therefore, seed your brand into relevant subreddits, get organic mentions in high-authority threads, and you'll show up in AI answers.

The advice wasn't wrong, exactly. It was engine-specific, and nobody said so.

ChatGPT does lean on Reddit. Suganthan's earlier teardown showed that. But Perplexity, according to his wire-level reads, retrieves Reddit threads into its candidate pool and then quietly drops them at the citation stage. Meanwhile YouTube — via transcripts, structured metadata, and a dedicated video surface — makes it through the pipeline and appears in the final citation list at a rate that dwarfs any other social platform.

If you're a UK service business optimising for "how AI search sees you," and you've been treating Perplexity and ChatGPT as roughly interchangeable, you've been optimising for one engine's preferences and paying for the effort in both. That's not strategy. That's guesswork with a monthly retainer attached.

The engines are diverging, and the industry hasn't caught up

Here's the part that matters more than the specific Reddit-vs-YouTube finding.

The engines are not the same product. They never were, and the divergence is accelerating.

For the last two years, the GEO conversation has treated "AI search" as a single surface with slightly different logos. ChatGPT, Perplexity, Gemini, Claude — everyone bundles them into a category and sells a category solution. Optimise your content for LLMs. Get cited. Build authority. It sounds like SEO but with new acronyms, which is what most of it actually is.

The engines are not the same product. They never were, and the divergence is accelerating.

Perplexity, per Suganthan's read, runs a 16-head query classifier that routes every question to a specific surface — maps, video, image, finance, shopping, how-to — with fixed thresholds. It fans out one round of conservative variants on your literal phrasing rather than generating a cloud of adjacent queries. It reads two to four full pages in Deep Research mode and lets those pages dominate citations. It has a written trust-note field, scoped per domain, that flags sources as "credible" or "trusted."

None of that is how ChatGPT works. And none of that is how Google's AI Mode works either. Three engines, three routing logics, three retrieval philosophies, three different definitions of what "getting cited" even means.

If you've been running a single GEO strategy across all three, you've been running a lowest-common-denominator strategy — which mostly means you've been running SEO, calling it GEO, and hoping the overlap is enough. Often it is. Often it isn't.

What the wire data actually tells you to do

Suganthan's piece is careful about confidence levels — structural findings from the wire are firm, percentages from an eight-capture sample are directional. That's the right way to talk about this. But even at the directional level, three implications are hard to ignore.

Optimise for the exact phrase, not the topic cloud. Perplexity's default fan-out is one conservative round of variants on the user's literal phrasing. If your content ranks for adjacent terms but not the exact query, you don't enter the candidate pool. This is a break from a decade of SEO advice that told you to write around a topic rather than for a keyword. In Perplexity's world, the keyword is closer to the truth than the topic. Not universally — Deep Research behaves differently — but for the standard commercial query, exact phrasing wins.

Video is a citation surface, not a marketing channel. If your business has been treating YouTube as a place to park brand videos for social proof, Perplexity's citation pattern is telling you something else. YouTube gets a dedicated retrieval slot for how-to queries. Transcripts get indexed and scored. A well-titled, well-transcribed YouTube video on a specific topic can appear in Perplexity citations for that topic in a way that no amount of blog optimisation can force. This is genuinely new leverage, and almost nobody in the UK small-business space is acting on it.

Reddit still matters — but only for ChatGPT. Don't abandon it. Do stop treating it as a universal GEO input. If you're serving a client whose customers use Perplexity for research (technical buyers, developers, high-consideration purchases), Reddit effort is misallocated budget. If they use ChatGPT, keep going.

The measurement point I keep having to make

I've written before about the measurement collapse in AI search — the fact that we're operating a discovery layer with almost no reliable telemetry. Suganthan's piece is a reminder that this problem has a specific structural cause, not just a tooling gap.

Every AI search engine is a black box with a proprietary retrieval pipeline. The pipelines are different. The signals they weight are different. The surfaces they route to are different. The citation logic is different. And none of them expose enough to let you optimise with confidence without doing what Suganthan did — literally reading the wire.

That's not a tooling problem GEO vendors can solve by selling you a prompt-tracking dashboard. Prompt tracking measures the output. It doesn't tell you why the output looks the way it does. The only way to know why is to read the retrieval stream, and the only person I've seen do that for Perplexity in public is Suganthan, once, in a single geo, on a single account.

That's the actual state of AI search measurement in 2026. One person, one browser, one afternoon of reverse-engineering.

Anyone selling you a comprehensive GEO monitoring platform is selling you a very expensive way to watch the surface of a system whose plumbing they cannot see.

What this means for your strategy this quarter

If you run a UK service business, or you advise ones, the practical read on this is narrow and specific.

First, stop paying for GEO strategies that treat all AI engines as one target. The retrieval logic is different enough that a single content investment will not perform equally across surfaces. Ask which engines your customers actually use. For most B2B UK service businesses, that's ChatGPT primary, Perplexity secondary, Gemini tertiary. For technical or research-heavy audiences, Perplexity moves up. The mix matters.

Second, if Perplexity is in your mix, invest in video. Not marketing videos — instructional, specific-question-answering videos with clean transcripts, accurate titles, and structured descriptions. A ten-minute video answering "how does [specific process] work in [specific context]" has a real chance of being cited by Perplexity in a way that a 2,000-word blog post on the same topic simply does not.

Third, audit your content for exact-phrase alignment on your money queries. Not just topical coverage — the literal wording your buyers use. Perplexity's fan-out is conservative. If your page uses jargon and the user uses plain language, you don't make the shortlist.

Fourth — and this connects to the brand monitoring point I made last week — track how you're being cited across engines, not just whether you appear. The same query on ChatGPT and Perplexity will pull different sources. If you only show up in one, you have an engine problem, not a content problem, and the fix is engine-specific.

The honest limits

Suganthan's sample is eight captures, one user, one geo. The structural findings are firm because you only need to see a field once to know it exists. The numeric findings — YouTube wins by how much, Reddit gets dropped at what rate — are directional. A larger sample in a different geo with different query mix would produce different percentages.

The bigger caveat is that Perplexity ships fast. Suganthan re-ran three captures four weeks after the originals and found the structure held except for one field. That's better than I'd have guessed, but it means anything specific I've said above has a shelf life. The direction of travel — engines diverging, retrieval logic getting more specific, citation surfaces multiplying — is what to hold onto. The specifics will move.

And it's worth saying: none of this makes traditional SEO less important. The pages Perplexity retrieves are pages Google surfaced first. Domain authority, technical hygiene, structured data, and clean information architecture are the ground floor. GEO tactics are the fittings on top. Anyone selling you GEO without SEO is selling you fittings without a floor.

The point of Suganthan's piece isn't that Reddit is dead or YouTube is the new frontier. It's that the industry has been operating on assumptions about how AI search works that don't survive contact with the actual wire data. The engines are more different from each other than the marketing suggests. The tactics that work on one don't transfer cleanly to another. And the only people who know this with confidence are the handful of practitioners willing to open their browser's network tab instead of buying a dashboard.

That's the loop we're in. A discovery layer worth billions of pounds of marketing spend, and the best public research on how it actually works is one consultant reading a live stream that disappears the moment it finishes.

Build for that reality. Not the one on the pitch deck.