SEO (Search Engine Optimization) targets Google's ranking algorithm. GEO (Generative Engine Optimization) targets AI systems that generate synthesized answers. AEO (Answer Engine Optimization) specifically targets the source-selection logic of AI answer engines like ChatGPT and Perplexity. All three are legitimate disciplines — they optimize for different systems with overlapping but distinct tactics.
SEO — optimizing for ranked lists
SEO has been the dominant web marketing discipline since the late 1990s. Its objective is to appear as high as possible in a ranked list of search results. The Google algorithm evaluates hundreds of signals — backlinks, page speed, content relevance, E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness) — and assigns a position. Success is measured by ranking position and organic click-through rate.
SEO remains essential. Google processes approximately 8.5 billion queries per day (2025 estimate). Even as AI assistants grow, traditional search remains the majority of web discovery traffic for commercial intent queries. SEO is not dead — but it no longer covers the full information surface.
GEO — optimizing for generative outputs
GEO was formally defined by Princeton researchers in a 2023 paper (Aggarwal et al., "GEO: Generative Engine Optimization"). It describes optimizing any content to appear in AI-generated responses, regardless of the specific system. GEO tactics include: adding statistics and quotable facts, citing primary sources, using authoritative language, and ensuring content is in AI training datasets. GEO is the broadest category — it applies to training-time inclusion as well as live web retrieval.
AEO — optimizing for answer engines specifically
AEO is a subset of GEO that focuses on answer engines: AI systems that respond to queries with synthesized answers and cited sources. ChatGPT (web search), Perplexity, Google AI Overviews, and Claude with web search are answer engines. AEO tactics are specifically about being selected as a cited source in these systems — not about appearing in training data or ranking in a list.
The AEO-specific elements that have no SEO equivalent include: llms.txt, agent.json, allowing AI crawler bots in robots.txt, and answer-first content structure optimized for excerpt extraction.
The overlap and the gaps
| Tactic | SEO | GEO | AEO |
|---|---|---|---|
| Backlink building | Core | Secondary | Secondary |
| Schema.org markup | Secondary | Important | Core |
| Answer-first content | Helpful | Core | Core |
| llms.txt | None | Helpful | Core |
| AI bot access (robots.txt) | None | Core | Core |
| Citation monitoring | None | Helpful | Core |
| Page speed | Core | Helpful | Helpful |
| Wikipedia / directory presence | Secondary | Core | Core |
Priority order for SMEs in 2026
For a business that has not invested in either discipline, the recommended order is:
- Fix technical SEO fundamentals — title tags, canonical URLs, page speed, structured data. These also help GEO/AEO.
- Implement AEO core signals — llms.txt, FAQPage schema, answer-first content on five key pages, AI bot access in robots.txt. These are one-time structural changes with compounding returns.
- Build GEO citation mass — Wikipedia presence, industry directory listings, press mentions, partner links. This is ongoing but high-leverage.
- Monitor and iterate — track both organic rankings (SEO) and citation frequency (AEO) on a weekly cadence.
The overlap between good SEO and good AEO is significant — a well-structured, fast, authoritative site performs better in both systems. The incremental AEO work (llms.txt, FAQPage schema, answer-first rewrites) is relatively small for a site already doing solid SEO.