An answer engine is a search system that responds to a question with a written answer and source links, instead of putting a list of results first. The term has no formal standard. Media use it often for Perplexity, and Google’s AI features are sometimes described the same way.
How does an answer engine work?
The system searches for pages that fit the question, a language model writes an answer from them, and links point to the sources used. Perplexity runs two bots for this. PerplexityBot is designed to surface and link websites in Perplexity’s search results. Perplexity-User visits a page to help answer a question when a person asks. Perplexity states that neither bot is used to crawl content for AI foundation models.
Google offers similar answers in Search through AI Overviews and AI Mode. Both may use a technique Google calls query fan-out, which issues several related searches across subtopics and data sources, so a wider and more diverse set of links can be shown.
| Term | Full form | Goal | Metric | Origin of the term |
|---|---|---|---|---|
| SEO | Search engine optimization | Help search engines understand content and help users find a site through search | Clicks, impressions, CTR and average position in the Search Console performance report | no clear first source; Google uses the term in its own documentation |
| GEO | Generative engine optimization | Increase the visibility of content in responses from generative search systems | in the research paper “Position-Adjusted Word Count” and “Subjective Impression”; for Google Search, impressions in the generative AI features performance report (since 2026-08-31) | Aggarwal et al., “GEO: Generative Engine Optimization”, arXiv:2311.09735 (2023-11-16), KDD 2024 |
| AEO | Answer engine optimization | Appear as a direct answer or source in answer systems (industry usage, no standard) | no defined metric | no clear first source |
| AI SEO | – | Umbrella term for SEO in AI-powered search, sometimes also for using AI tools in SEO work (industry usage) | no defined metric | no clear first source |
| LLMO / LLM SEO | Large language model optimization | Be mentioned in answers from large language models (industry usage, often used interchangeably with GEO) | no defined metric | no clear first source |
The table describes terms and does not rate methods. For AI Overviews and AI Mode, Google names no requirements beyond the basics of Search. The terms GEO, AEO and LLMO do not appear in Google's documentation on AI features. Goals without a primary source reflect industry usage. Sources: Aggarwal, P. et al.: GEO: Generative Engine Optimization. arXiv:2311.09735 (2023), KDD 2024; Google Search Central: SEO-Startleitfaden / SEO Starter Guide; Search-Console-Hilfe: Leistungsbericht (Suche) / Performance report (Search); Search-Console-Hilfe: Leistungsbericht zu generativen KI-Funktionen (Google Suche); Google Search Central: KI-Funktionen und deine Website / AI features and your website. Last checked: .
What does it mean for SEO?
Google states that no additional requirements apply for appearing in AI Overviews or AI Mode. Pages have to be indexed and eligible for snippets. Traffic from these features is included in the Web search type of the Performance report in Search Console. For other answer engines, their bots must be able to reach and read a page (Assumption).
Example
For the question “How long do roof tiles last?” an answer engine writes a short text with ranges for different materials. Links next to single statements lead to the pages the information came from. Clicking one opens the source.
FAQ
Which products count as answer engines? Perplexity and Google’s AI Mode are often named. No fixed list exists.
How does an answer engine differ from a chatbot? An answer engine retrieves current sources for its answer and shows them. A chatbot without web search answers from the model’s training data (Assumption).
Sources
- Perplexity bots (PerplexityBot, Perplexity-User) – Perplexity Docsdocs.perplexity.ai
- AI features and your website – Google Search Centraldevelopers.google.com
- Expanding AI Overviews and introducing AI Mode – Google Blogblog.google
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