Definition
PerplexityBot indexes pages so they can be surfaced and linked in Perplexity answers. Perplexity's documentation states it is not used to crawl content for foundation models. A second agent, Perplexity-User, visits a page because a user's question requires it.
Why it matters
Perplexity cites sources on nearly every answer, so a block here shows up in citation data faster than anywhere else. It is the engine where an access mistake is cheapest to detect and most expensive to leave in place.
How to measure it
Watch your own domain's appearance in cited sources over a fixed question set. Count only URLs marked in the answer body — the retrieval candidate pool is much larger than what gets cited, and counting it inflates the figure several times over.