What Is an AI Visibility Index?

What Is an AI Visibility Index?

Definition: An AI visibility index is a metric that shows you how many times your brand is mentioned, and how much weight it carries, in AI generated responses relative to competitors. This is done by using a standardised set of prompts to ask AI engines questions and measure how many times the brand is mentioned or cited. The data is then scaled to allow brands to be compared and monitored over time.

An index is a benchmark, so it answers “how do we compare?” A single tracked metric answers “how are we doing?” Some indexes are published studies of a whole industry. Others are scores inside a product.

How Are AI Visibility Indexes Built?

Most follow the same steps:

1. 1. Pick a prompt set. This could be questions asked by buyers in relation to a category (not specific to any particular brand).
   2. Pick the engines. This is typically ChatGPT, Gemini, Perplexity and Google’s AI surfaces.

1. Run the prompts, usually more than once, and record each answer.
2. Count what appears. Brand mentions, cited sources, position in the answer, or all three.
3. Scale the result. Convert counts into a share or a 0 to 100 score so brands can be compared.

Where they differ is in the prompt set, the engines, what gets counted and how it’s scaled. That’s why scores from different indexes can’t be compared directly.

How Do the Main Public AI Visibility Indexes Compare?

Index	Published by	What it measures	Engines	Format	Checked
Semrush AI Visibility Index	Semrush (an Adobe company)	Brand mentions and cited domains across 22 industries. The 2026 edition analyzed 126 million US prompts (Jan to Apr 2026) and 1,200+ brands	ChatGPT, Gemini, Google AI Mode, Google AI Overviews	Published study, first published in 2025	Nov 11, 2026
Similarweb Generative AI Brand Visibility Index	Similarweb	Brand mention share across six sectors and 113 brands, using January 2026 US data, plus a separate momentum index	ChatGPT, Gemini, Copilot, Perplexity	Published report (March 2026). Category leaders show 100	Nov 11, 2026
Evertune AI Brand Index	Evertune	AI Brand Score: how often your brand is mentioned, weighted by position, on prompts that don’t name it	ChatGPT, Gemini, Claude, Meta, AI Overviews, Perplexity, Copilot and others	0 to 100 score inside a platform	Nov 11, 2026
5W AI Visibility Index	5W Public Relations	Citation share of brands by category, published category by category	ChatGPT, Claude, Perplexity, Gemini, Google AI Overviews	Published research series. 5W’s methodology calls the scores benchmarks, not deterministic measurements	Nov 11, 2026

The Semrush index is a study. It is separate from the AI visibility tools Semrush sells. Similarweb and 5W also publish theirs as research.

What Does an Index Score Look Like in Real Data?

Index entries are usually a count turned into a share. In 5W’s Consumer Brands Index 2.0 (published 13 August 2026), each brand is scored on 288 answers from four AI engines:

Brand	Answers naming the brand	Share	95% interval
L’Oréal	116 of 288	40.3%	34.8% to 46.0%
Unilever	67 of 288	23.3%	18.8% to 28.5%

Share = answers that name the brand ÷ total answers. The interval shows how much the share could move with a different sample. Because these two intervals don’t overlap, L’Oréal’s lead is clear. When intervals overlap, 5W says no sole leader is established. A rank alone can overstate a small gap.

Source: 5W Consumer Brands Index 2.0. One category, one set of prompts, one measurement window.

How Does a Brand Read Its Own Index Score?

• Compare like with like. Only compare scores from the same index, prompt set and period.
• Read it as relative. Scores are usually relative to a category or a leader. Similarweb’s category leaders show 100, and Evertune uses a 0 to 100 scale. A score of 40 means different things in each.
• Check the engines. A strong score on one engine can hide a weak one. Semrush’s 2026 study found only 36 brands kept top-100 visibility on every platform across the whole study.
• Separate mentions from citations. Semrush found that fewer than half of the top 100 mentioned brands were also among the top 100 cited domains.
• Treat it as a sample. AI answers vary run to run, so one reading is a snapshot. See how AI answer variability impacts SEO.
• Watch the trend. A single score shows position and not direction. See AI visibility momentum.

How Does the Wellows Score Map to These Indexes?

Public indexes benchmark categories. The Wellows score tracks your brand. The two answer different questions, so there’s no direct conversion between them.

	Public indexes	Wellows score
Scope	A category or industry, across many brands	Your brand and your tracked competitors
Prompts	The publisher’s prompt set	The prompts you track
What’s counted	Mostly brand mentions, sometimes citations or position	Citations: your domain cited directly, and third-party pages that mention you
Refresh	Periodic, from monthly to quarterly or per edition	Daily, across ChatGPT, Gemini, Perplexity, Google AI Overviews and AI Mode
Best for	Category context and benchmarking	Tracking and acting on your own gaps

The Wellows Citation Score combines direct citations (AI cites your domain) and inherited citations (AI cites third-party pages that mention you). It is weighted by query intent and competitor share of voice. The AI Visibility Score shows your share of total citations against competitors across your tracked prompts. Use public indexes for context and your own tracked data to see what to change.

Conclusion:

An AI visibility index gives you category context: where you stand against competitors on one set of prompts. It doesn’t tell you what to fix or which way you’re heading. Use public indexes to benchmark, compare scores only within the same index and period, and track your own mentions, citations and trend over time.

See how AI describes your brand today with the free AI Brand Report.