Semrush data: Google, ChatGPT and Gemini barely agree in the UK

Semrush's expanded 2026 AI Visibility Index shows that ChatGPT, Gemini, Google AI Mode and Google AI Overviews agree far less in the UK than in the US on which brands to mention and which sources to cite. In the UK, any two platforms shared only 63 to 70 of their top 100 mentioned brands, compared with 70 to 78 in the US, and fewer than half of the UK's top mentioned brands also turned up among the most-cited sources. The message for any business tracking AI visibility is blunt: ranking well on one AI platform tells you almost nothing about how you're doing on the others, and that gap is worse outside the US.

What changed?

Semrush released the latest edition of its 2026 AI Visibility Index on 13 October 2026, presented at Spotlight London. The new report expands the firm's flagship research with, as Semrush puts it, a dedicated comparison on how major AI platforms surface brands and sources in the UK and US.

The study is large. It covers seven months (January to July 2026) of AI visibility data across fixed monthly sets of 2.5 million UK and 25 million US prompts, built from Semrush search data, across ChatGPT, Gemini and Google AI Mode, alongside a larger variable dataset of Google AI Overviews results for real search keywords. That builds on the original version of the Index, which Semrush said scaled up from an initial 2,500-prompt sample to 126 million US AI search prompts analysed from January through April 2026.

The headline finding is consistency, or rather the lack of it. Across all seven monthly benchmarks, the four AI platforms agreed less in the UK than in the US on which brands to mention and which sources to cite. According to The Next Web's reporting on the data, on average, any two of the four platforms shared 63 to 70 of their top 100 mentioned brands in the UK, and UK platforms agreed less on both brands and sources in all seven months measured.

Being named by an AI assistant and being cited as a source for that answer are two separate things. Fewer than half of the top 100 mentioned brands also appeared among the top 100 cited domains, on average across categories and platforms. In the UK, that overlap ranged from 36.7 to 45.3 domains out of 100, depending on the month.

Platforms also differ sharply in how many sources they lean on and where they get them. The study found that Gemini mentions more distinct brands per answer than ChatGPT, while ChatGPT cites the most sources per answer of the four platforms studied. News publishers play an outsized role in the UK specifically: according to The Next Web, news and information sites took 29.5% of citations among ChatGPT's 100 most-cited UK domains, on average, against 19.6% in the US.

Only a small set of brands show up reliably everywhere. Coverage from MarTech Series notes that 24 UK domain records met the standard of appearing across all four platforms every month, compared with 36 in the US, with only 15 domains shared across both markets, including Adobe, Apple, Amazon, Google, LinkedIn, Microsoft, Reddit, TikTok and YouTube.

Why does this matter for your business?

If you're a UK brand assuming that strong ChatGPT visibility means you're also doing well on Gemini or Google's AI Mode, this data says otherwise. The fragmentation is structural, not a quirk of one category: it shows up across all seven months and every platform pairing Semrush tested.

It also means a single "AI SEO" strategy aimed at one assistant won't travel far. A brand optimised for the US market, where platform agreement is higher, cannot assume the same approach works in the UK. As one analysis of the report, from Techi, put it: a UK strategy cannot simply inherit the US score, because the report identified 24 UK domain records and 36 US records that appeared in all four platforms' top-100 mention lists in every month, with only 15 domain records belonging to both groups.

The gap between being mentioned and being cited matters commercially too. If an AI assistant names your brand in passing but never links to or cites your site as a source, you get brand exposure without the traffic, trust signal or attribution that a citation carries. Semrush's wider dataset shows this gap can be severe: on Gemini, the overlap between mentioned brands and cited domains can be as low as 30%, reinforcing the need for brands to compete on two fronts: earning enough authority and relevance to be mentioned, while also creating credible, structured content that AI platforms can cite.

For sectors with heavy UK media consumption, the reliance on news sites changes the playing field again. A brand chasing citations purely through product pages or landing pages is competing against an entrenched pool of UK news and information domains that already dominate ChatGPT's citation pool in that market.

What should you do now?

Start by checking where you actually show up, not where you assume you show up. Given how little overlap there is between platforms, a brand that looks strong on one AI assistant could be close to invisible on another, and the only way to know is to test across all of them separately. This is exactly the kind of gap worth checking with your own AI visibility audit: Sited's free audit will show you, platform by platform, whether you're being mentioned, cited, both or neither.

Second, treat "mentioned" and "cited" as two different goals that need two different tactics. Being mentioned is often about brand recognition and entity clarity: making sure AI systems understand who you are and what you do. Being cited is about having content structured and credible enough that an assistant pulls a direct quote or fact from your page rather than paraphrasing from memory.

Third, if you operate in the UK, don't assume US-focused GEO advice applies unchanged. The Semrush data suggests UK brands face a more fragmented landscape with a stronger pull towards news and information sites in citation pools, so earning coverage or mentions on relevant UK publications may do more for AI visibility than it would in the US market.

Finally, revisit this kind of benchmark regularly. Semrush's own data shows month-to-month movement in the overlap figures, which means AI visibility isn't a one-off project: it needs the same ongoing monitoring that SEO teams already apply to rankings.

Frequently asked questions

What is the Semrush 2026 AI Visibility Index?

It is a large-scale benchmark study from Semrush that analyses seven months of AI visibility data across fixed monthly sets of 2.5 million UK and 25 million US prompts, across ChatGPT, Gemini, Google AI Mode and Google AI Overviews, tracking which brands get mentioned and which sources get cited.

Why do UK and US results differ so much?

Semrush's data shows the four platforms draw on different pools of brands and sources depending on the market, with any two platforms sharing only 63 to 70 of their top 100 mentioned brands in the UK, versus 70 to 78 in the US. The exact cause isn't stated in the report, but the pattern held across all seven months studied.

Does being mentioned by an AI assistant mean you're also being cited?

No. Semrush found these are separate outcomes, and in the UK the overlap ranged from 36.7 to 45.3 domains out of 100, depending on the month, meaning more than half of mentioned brands typically aren't cited as sources.

Why do news sites feature so heavily in UK citations?

Semrush's research found that on ChatGPT specifically, news and information sites took 29.5% of citations among its 100 most-cited UK domains, compared with 19.6% in the US, suggesting UK AI answers lean more heavily on established media outlets than their US equivalents.

What should a marketing leader do with this data?

Audit your visibility on each AI platform separately rather than assuming consistency, and focus on both brand recognition, to be mentioned, and citable, well-structured content, to be cited, since Semrush's research treats these as distinct challenges requiring different tactics.