GEO vs AEO vs AIO vs SEO: What the Terms Mean and Which One You Need (2026)
By Alexey Chasin · Updated September 25, 2026 · 8 min read
SEO is ranking in a list of search results. GEO, generative engine optimization, is being cited inside answers generated by ChatGPT, Claude, Gemini and Perplexity. AEO, answer engine optimization, is being the direct answer in Google's AI Overviews, AI Mode and featured snippets. AIO, LLMO and GSO are other names for the same work. No standards body separates the terms, and Wikipedia recorded in early 2026 that they are used interchangeably. The practical difference is the engine you are checking. The work is the same: answer first, definitive language, original numbers, structured data, crawler access and third-party mentions. A local business needs all of it, and it comes as one job.
The definitions
| Term | Stands for | Where you win | What 'winning' looks like |
|---|---|---|---|
| SEO | Search engine optimization | Google, Bing result lists | Your page is in the top results and gets the click |
| GEO | Generative engine optimization | ChatGPT, Claude, Gemini, Perplexity | Your business is named or your page is cited in the generated answer |
| AEO | Answer engine optimization | Google AI Overviews, AI Mode, featured snippets, voice assistants | Your page is the direct answer shown above or instead of the results |
| AIO | AI optimization | All of the above | Umbrella term; used for audits and services that cover every engine |
| LLMO | Large language model optimization | ChatGPT, Claude, Gemini as chat | Same as GEO; used by tool vendors |
| GSO | Generative search optimization | AI search features | Same as GEO and AEO; rare outside vendor copy |
Why the terms overlap
Every AI answer engine does the same three things: retrieve pages from a search index, read them, and write an answer that quotes the ones it trusts. Google's AI Overviews and AI Mode retrieve from Google's index. ChatGPT's search retrieves from Bing's. Perplexity runs its own crawler. So the engines differ in where they look, and the page that gets cited by all of them looks the same: it answers the question in the first 100 words, uses definitive language, contains original numbers, is marked up so the business is a clear entity, is allowed to the crawlers, loads fast, and is backed by mentions on Reddit, LinkedIn and review sites. Frase, Jasper, Writer and the other 2026 guides all land on that list, whichever acronym they use for it.
Where the terms genuinely differ
- GEO is about conversations. Someone asks ChatGPT 'who should I hire to build my dental website in San Diego' and gets three names. Winning is being one of the names. Third-party mentions weigh most here, about 6.5 times more than your own site across the 2026 studies.
- AEO is about the answer box. Someone Googles 'how much does a website cost in San Diego' and the AI Overview says '$3,000 to $8,000' with a source link. Winning is being the source. Ranking on the page already and answering early weigh most here; Contently's 2026 study found AI Overviews cite pages that already rank for the query.
- AIO is the audit. When a service says AI search optimization or AIO, it means checking and fixing all of the above across every engine, and reporting citations monthly.
Which one a local business needs
All of it, as one job, and not as three invoices. The plumber in Escondido needs to rank for 'plumber Escondido' (SEO), to be the answer in the AI Overview for 'water heater cost Escondido' (AEO), and to be one of the names when someone asks Gemini for a plumber (GEO). The same thirty pages, written answer-first with prices and FAQs, marked up and crawlable, backed by reviews and a Business Profile, do all three. Anyone selling GEO as a separate line item from SEO is charging twice for one thing.
What each engine reads
| Engine | Retrieves from | Crawler to allow | Extra signal |
|---|---|---|---|
| Google AI Overviews and AI Mode | Google's index | Googlebot, Google-Extended | Pages already ranking; Business Profile for local |
| ChatGPT search | Bing's index plus its own fetches | GPTBot, OAI-SearchBot, Bingbot | Reddit and LinkedIn mentions; Bing Webmaster Tools submission |
| Gemini | Google's index | Googlebot, Google-Extended | Same as AI Overviews; entity consistency |
| Perplexity | Its own crawler and index | PerplexityBot | Fresh pages; clear headings and citations |
| Claude | Web search when enabled | ClaudeBot | Definitive, well-structured answers |
If a page is blocked to one crawler, it cannot be cited by that engine no matter how good it is. Our guide to AI crawlers, robots.txt and llms.txt covers the exact lines to add.
How to check where you stand
Type your service and city into Google and note whether an AI Overview appears and who it cites. Ask ChatGPT, Gemini and Perplexity for a recommendation in your category and city and note who is named. Search your business name in each and note whether the description is right. That is a ten-minute AIO audit, and the gap between the answers you got and the ones you want is the work. Our fixed-price audit does the same across thirty prompts and reports the fixes in order.