OpenAI has reported 159.1 million average monthly search recipients in the EU, crossing the threshold that triggers very large online search engine status under the Digital Services Act. That is a regulatory designation, not a marketing claim. It puts ChatGPT alongside Google and Bing in terms of the compliance obligations and transparency requirements the EU can impose. For anyone running an AEO or GEO programme, the number itself matters more than the legal category.
159 million monthly users conducting searches is not a niche behaviour. It is a mainstream information-seeking channel, and the EU figure almost certainly underrepresents global usage. If your brand is not actively working to earn citations and recommendations inside ChatGPT, you are already absent from a channel at scale.
Scale Changes the Prioritisation Conversation
One of the persistent objections to investing in AI search visibility has been uncertainty about audience size. Teams could reasonably argue that Google AI Overviews, with its existing user base, deserved the budget and attention first. That argument gets harder to sustain when a single competing platform reports 159 million monthly search users in one region alone.
The practical consequence is that ChatGPT now belongs in your channel mix with a dedicated visibility strategy - not as an afterthought bolted onto your Google AEO work. The two platforms extract and cite information differently. Treating them as interchangeable will produce mediocre results on both.
Perplexity has been building its own scale separately, and Gemini sits inside Google's ecosystem. The picture across AI search overall is of several large, distinct surfaces each pulling from different source pools with different ranking mechanics. Brand visibility in one does not guarantee visibility in another.
What ChatGPT Actually Pulls From - and Why It Matters for Citations
ChatGPT's search functionality draws on web crawling via its own bot, Bing's index, and the training data underlying the model. That blend means citations can surface from a wider range of sources than a traditional search result - including forum posts, third-party review platforms, publisher coverage, and structured data embedded in your own pages.
Digital PR plays a specific role here. When your brand earns coverage on credible, indexed publications, that content becomes part of what ChatGPT can retrieve and surface. A brand that exists only on its own domain - no external mentions, no third-party validation - is far harder for the model to recommend with confidence. The citation logic is not identical to Google's link graph, but the underlying principle is similar: corroboration from external sources builds credibility.
Schema markup and structured content still matter, but ChatGPT's extraction is more tolerant of unstructured prose than Google's featured snippets were. Clear, factually dense content that directly answers specific questions remains the baseline requirement. If your pages bury answers in filler or require significant inference to extract a usable fact, they will be overlooked in favour of sources that are more direct.
Regulatory Status Brings Transparency Obligations - Which Helps Measurement
The DSA classification requires platforms like ChatGPT to publish detailed data on their user numbers and, in some cases, their systems. That is not directly useful for citation measurement, but it does signal a direction of travel: AI search platforms are moving towards greater accountability and discoverability of their mechanics. For measurement teams, this matters.
Right now, attributing traffic and leads from ChatGPT relies on identifying referral sessions in GA4 tagged with ChatGPT as the source, and tracking UTM parameters where you control the linked content. It is imperfect. Many AI-referred visits arrive with no referrer string because the user copies a URL from a response rather than clicking through. You catch those through CRM-level attribution - asking at lead submission which channel prompted the enquiry, and cross-referencing with any direct traffic spikes that correlate with brand mentions in AI tools.
As regulatory pressure increases on these platforms, there is a reasonable expectation that structured referral data will improve. In the meantime, the gap between actual AI-referred revenue and what your analytics tools report is almost certainly wider than you think. Building manual audit processes now - checking ChatGPT, Perplexity, and Gemini for brand mentions on a monthly basis - gives you a baseline before better data becomes available.
Crawler Access Is Non-Negotiable at This Scale
With ChatGPT confirmed at this kind of user scale, blocking its crawler is a meaningful commercial decision, not a technical default. Many sites inherited robots.txt rules that were written before AI search crawlers existed, and those rules may be inadvertently blocking ChatGPT's bot, GPTBot, from indexing content that could earn citations.
The audit is straightforward. Check your robots.txt for any rules disallowing GPTBot. Check whether you have an llms.txt file in place that signals to AI crawlers which content is most useful to index. If neither has been reviewed in the last six months, the odds are reasonable that your crawler access policy does not reflect your current AI visibility goals.
This is not about opening your entire site indiscriminately. It is about making a deliberate decision: which content do you want AI search surfaces to find and cite, and have you made it technically accessible? At 159 million monthly search users in the EU alone, the audience on the other side of that decision is not trivial.
What to Do This Quarter
Start with a visibility audit across ChatGPT, Perplexity, and Google AI Overviews for your ten highest-value search queries. Check whether your brand appears, and if it does, whether it is being cited accurately. Note which competitors appear in your place. That audit gives you a concrete gap to close, not a vague objective to pursue.
Map your current digital PR output against the topics where you want AI citation. If you are winning coverage in publications that ChatGPT's crawler can access, those placements are doing double duty - traditional SEO value plus AI citation potential. If your PR coverage is thin or confined to paywalled outlets, that gap is directly affecting your AI search presence.
Finally, brief your CRM and lead intake team on AI search attribution. Add a question to your lead forms - or your sales discovery calls - that asks how the prospect found you. When someone says ChatGPT or a similar tool, log it explicitly. That qualitative data, combined with referral tracking, is currently the most reliable way to understand what AI search visibility is actually worth to your business. The channel is now too large to measure loosely.