What Is a Visibility Index?

A visibility index is a composite score — usually 0-100 — that aggregates a brand's presence across many AI prompts, engines, and sampling runs into a single trendable number. It is the AI-era analogue of SEO visibility indices like Sistrix's: nobody can act on 500 prompt-level data points weekly, but everybody can act on "the index dropped 12 points after the model update."

The weighting choices behind the number

Every index embodies editorial decisions, and understanding them is prerequisite to trusting the score:

• Component weights — how much mention rate counts versus answer position versus citation share versus sentiment. An index weighted toward citations rewards content strategy; one weighted toward mentions rewards brand fame.
• Prompt weights — commercial-intent prompts ("best X for Y") usually count more than informational ones, mirroring how SEO indices weight keywords by search volume. Prompt importance is an estimate, since platforms publish no prompt-volume data.
• Engine weights — weighting by estimated user base (ChatGPT's hundreds of millions of weekly users versus smaller engines) versus equal weighting changes rankings materially.
• Normalization — against a fixed scale, or relative to the competitor set so the index reads as market share.

Because these choices differ per vendor, cross-tool index comparisons are meaningless; within-tool trends are the valid signal.

Reading an index correctly

Three usage rules. Treat sudden index moves as triage triggers, then diagnose at the component level — a drop concentrated in one engine after a model swap is an engine event, not a content failure. Annotate model updates and prompt-set changes on the trend line, since both break comparability. And pair the index with a competitor version: an index falling while every competitor's falls equally describes the engine; falling alone describes you.

Example

A martech brand's index fell 9 points in a week. Component drill-down showed mention rate flat but citation share collapsed — one engine had shifted citations toward review aggregators category-wide. The response was a review-platform push, not a website rewrite. That diagnostic path, index → component → action, is how visibility scoring is meant to be used.