GEO glossary

Perplexity

Perplexity is an AI answer engine that searches the web in real time and writes a direct answer to a question, with numbered footnotes linking to the sources it used. It runs its own search index and crawler, PerplexityBot, so visibility in Perplexity depends on being crawled and retrieved by it.

Reviewed by Gareth Hoyle, Managing Director
Last reviewed 31 October 2026

How does Perplexity answer a question?

Perplexity's help centre says it uses AI to search the internet in real time and that every answer includes numbered footnotes linking to the original sources, so readers can check a claim. Because answers are written from retrieved pages, Perplexity is a retrieval-augmented generation system: the pages it finds shape what it says. In machine learning, perplexity is also the name of a metric for how well a model predicts text, which is unrelated.

Which index and crawler does Perplexity use?

When Perplexity opened its Search API to developers in September 2025, it said the API gives access to the same global-scale infrastructure that powers its public answer engine, with an index covering hundreds of billions of webpages and tens of thousands of index updates processed every second. Documents are divided into fine-grained units, each scored against the query.

Its documentation names two user agents. PerplexityBot is designed to surface and link websites in Perplexity's search results and is not used to crawl content for AI foundation models. Perplexity-User visits a page when a user's question needs it, and because a person requested the fetch, it generally ignores robots.txt.

What Perplexity means for AI visibility

Perplexity is one of the easiest assistants to audit, because its sources are always listed. In an August 2025 Ahrefs study, 28.6% of the URLs it cited ranked in Google's top 10 for the same prompt, the highest of the assistants tested, so most of its citations still came from elsewhere.