Why it matters
Pick the 30 prompts your buyers actually ask — spec questions, cross-reference lookups, “best supplier for X” — run them across engines, and count how often each brand appears. The resulting share is a clearer category scoreboard than keyword rankings, because it measures the surface buyers now act on.
How to measure it
Define a stable prompt set, sample each engine repeatedly (answers vary per run), and track your mention and citation counts against named competitors over time.
In practice
An industrial e-commerce distributor uses Ahrefs' Brand Radar 'AI Share of Voice' report to track how often it is named versus rivals when buyers ask AI engines its own prompts, such as 'best hydraulic hose supplier' or 'NPT vs BSPP fitting cross-reference.' Per Ahrefs, the metric is the percentage of brand impressions (mentions weighted by Google search volume) a brand owns across ChatGPT, Perplexity, Gemini, Copilot, and Google AI Overviews/AI Mode, refreshed monthly over a 90-day window.
Source: ahrefs.com