Share of model
Definition
Share of model is the percentage of relevant AI-generated answers in which your brand appears, measured across a defined set of prompts and platforms. It is the AI-search equivalent of share of voice and the headline metric for tracking GEO performance.
How it works
Share of model is calculated by running a representative set of prompts against multiple AI platforms — typically ChatGPT, Claude, Perplexity, and Google AI Overviews — and counting how often your brand is mentioned in the responses, divided by the total number of prompts where any competitor in your category appears.
The formula is straightforward: prompts mentioning your brand, divided by prompts mentioning any tracked competitor, multiplied by 100.
Why it matters
Click-through rate is collapsing as AI Overviews and chat-based search absorb more queries. Share of model captures the visibility you are losing in traditional analytics — the answers users see and act on without ever clicking a link.
47%
Of Google searches now show AI Overviews
BrightEdge, 2026
900M
Weekly active users on ChatGPT
OpenAI, Q1 2026
25–40%
Higher conversion from AI-referred traffic vs organic search
Indexly research, 2026
How to measure it
Define a prompt set of 50–500 queries that reflect how your buyers actually search. Run them weekly across each platform, parse responses for brand mentions, and track the rolling 30-day average. Indexly automates this end-to-end.
How to improve it
The fastest improvements come from publishing answer-ready content for your highest-priority prompts, building entity authority through consistent brand mentions across the open web, and ensuring your site is crawlable by GPTBot, ClaudeBot, and PerplexityBot.
Frequently asked questions
Is share of model the same as share of voice?
No. Share of voice measures presence in human-generated channels — press, social, ads. Share of model measures presence in AI-generated answers, which behave differently and require a different optimization stack.
How many prompts do I need to track?
A statistically meaningful baseline starts at 50 prompts. Most brands graduate to 200–500 prompts segmented by buyer journey stage and intent.
Does share of model differ across AI platforms?
Significantly. Only 11% of domains are cited by both ChatGPT and Perplexity, so brands often have wildly different share figures across platforms and need to optimize for each.
AI share of voice
AI share of voice is your brand's proportion of mentions in AI-generated responses relative to competitors, measured across a defined set of prompts and platforms. It adapts the traditional share of voice metric for AI search — where visibility lives inside chat answers and AI Overviews rather than ranked links or media impressions.
Citation probability
Citation probability is the likelihood that an AI system will cite a specific URL when generating a response to a target prompt. Unlike share of model, which measures brand visibility across a prompt set, citation probability is a per-URL metric — it tells you how strong an individual page is at earning citations.
AI visibility score
The AI visibility score is a single composite number — typically on a 0–100 scale — that summarizes a brand's standing across AI assistants (ChatGPT, Claude, Gemini, Perplexity, Grok, AI Overviews) by blending mention frequency, citation rate, ranking position, sentiment, and AI-referred traffic. It is the executive-friendly headline metric for Generative Engine Optimization (GEO) programs.