Semrush AI Visibility Index by country: what it measures

By Redacción Usanzia · Published 27 October 2026

Semrush's AI Visibility Index tracks which brands ChatGPT, Gemini, AI Mode and AI Overviews mention and which domains they cite, by market, month and industry, with no overall score. The October 2026 edition only compares the UK and US. For Spain and other markets, Semrush offers data in its paid tool, with a different metric.

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What is Semrush's AI Visibility Index?

The AI Visibility Index is a Semrush study and interactive explorer showing which brands appear in AI platforms' answers and which sources those answers cite. According to its methodology page, it covers 180M+ AI answers across 22 industries, nine markets and four platforms: ChatGPT, Google AI Mode, Google AI Overviews and Gemini.

There's no global ranking. Semrush shows results by market and month, separately for each platform, with no combined visibility score. A month is only included when data exists for all four platforms, so the available months vary by market.

AI doesn’t recommend the same brands everywhere.

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What exactly does it measure, and how?

The index measures mentions and citations, not traffic or conversions. The metrics Semrush defines in its methodology are:

• Mentions: how often a brand is named in AI answers.
• Citations: how often a domain is cited as a source in those answers.
• Brand co-occurrence: how often two brands appear together, relative to the selected brand's mentions. It's a ratio and can exceed 1.
• Top 100 overlap: how many entries two top 100 lists share, such as the most-mentioned brands on two platforms.

Semrush ranks brands by mention count and sources by citation count within each market, month, industry and platform. Cross-platform comparisons count shared entries between two lists, not whether they hold the same ranks.

The prompts come from Semrush's AI search database, which the methodology says holds 317M+ unique prompts. They're built from AI search clickstream data, including the clickstream provider Datos, and from Google's AI Overviews keyword dataset, then deduplicated and grouped by topic.

Which countries does it cover?

The methodology page mentions nine markets but doesn't list them, and the latest edition only compares the UK and US. According to the 13 October 2026 press release, the H2 edition covers seven months (January to July 2026) with fixed monthly sets of 2.5 million UK prompts and 25 million US prompts for ChatGPT, Gemini and AI Mode. On top of that is a larger, variable dataset of AI Overviews results for real search keywords.

As far as we could check, the index doesn't publish data for markets such as Spain. Don't confuse it with Semrush's paid AI Visibility Toolkit: according to its knowledge base, the Visibility Overview, Competitor Research and Prompt Research reports cover 42 listed regions, Spain among them, plus a worldwide view.

What does the October 2026 edition say about the UK and US?

Semrush's headline conclusion is that there's no single global route to AI visibility. These figures come from the 13 October 2026 press release:

• Platforms agree less in the UK. On average, any two platforms shared 63 to 70 of their top 100 mentioned brands in the UK, versus 70 to 78 in the US.
• News carries more weight in the UK. On ChatGPT, news sites accounted for an average 29.5% of citations among the 100 most-cited UK domains, versus 19.6% in the US.
• A small shared core. 24 domains in the UK and 36 in the US were in the top 100 mentions on all four platforms every month. Only 15 were shared across both markets.
• Mentioned isn't cited. On average across 22 industries and four platforms, fewer than half of the top 100 mentioned brands were also among the top 100 cited domains, every month and in both markets. In the UK, average overlap ranged from 36.7 to 45.3 domains out of 100.
• Concentration differs by platform. In the UK, AI Mode's ten leading source domains accounted for 23.2% to 35.8% of citations among its 10,000 most-cited domains, versus 12.8% to 15.4% for ChatGPT.

The useful takeaway isn't any single figure but the pattern: if two closely related English-speaking markets differ this much, don't extrapolate US or UK data to other markets. Aleyda Solis made the same point on X when sharing the index update: despite the shared language, the sources and brands the platforms show differ by market and are clearly localised, so she urged people to "think twice" before assuming what works in the US will work in other English-speaking markets (her post, 26 October 2026).

What are its limitations?

The index is useful for spotting patterns, but keep these limitations in mind before quoting it:

• It's published by a vendor. Semrush sells AI visibility tools, and the press release ends by promoting them.
• Prompts aren't one-to-one real conversations. They're built from search and clickstream data, deduplicated and grouped by topic.
• AI answers vary. The methodology itself asks you to read each month as a snapshot and not to treat month-to-month differences as growth or decline on their own.
• Coverage figures don't always match. In May 2026, Semrush cited 32 countries and 261 million prompts in its database; its knowledge base now mentions 117 regional databases and 317M+ prompts. That may reflect growth and different ways of counting, but it's a reason to always quote the date.
• Semrush describes the AI Visibility Score in two ways. Its article on where its data comes from refers to topic coverage and mention consistency; its AI Visibility Toolkit article refers to mentions compared with the competitors' median. We use the first.
• We read the press release and the website, not the full report, which sits behind a download form. We don't use the homepage statistics (such as LLM users' conversion rates) because the page doesn't link their source.

Trust and evidence

• Primary sources: the AI Visibility Index methodology page, the index homepage, Semrush's press release of 13 October 2026, the press release of 14 May 2026, and Semrush's knowledge base articles on the AI Visibility Toolkit and where its data comes from. All checked on 27 October 2026.
• Original testing: we haven't run our own test for this article (we haven't used the paid tool or downloaded the full report).
• Method and limitations: every primary source comes from Semrush, which has a commercial interest in the topic. We only quote figures Semrush has published, with their dates, and we separate declared methodology from our own interpretation. We couldn't confirm which nine markets the index covers.