What is the difference between AEO, GEO and SEO, and which do you need?

What do AEO, GEO and AI SEO each mean?

Answer engine optimization (AEO) means shaping pages so an engine can lift a direct answer from them. Generative engine optimization (GEO) means being named or cited inside an answer that an AI model writes. AI SEO is the market's catch-all for both. Google notes that people call this work AEO or GEO, and its guide files the work under SEO⁷¹.

The term GEO also has an academic origin. A 2023 paper tested ways of rewriting content so that generative engines pick it up, and reported visibility gains of up to 40 percent on the authors' own benchmark³. A benchmark is a lab test. It is not a promise about your site.

Does Google treat AEO and GEO as separate from SEO?

No. Google's guide says optimizing for generative AI search is optimizing for the search experience, and that SEO best practices stay relevant because its AI features rely on its core ranking and quality systems¹.

Google also lists what you do not need: no new machine-readable files, no AI text files and no special schema markup for its AI features². Its guide adds that Google Search does not use llms.txt files, that adding one will neither help nor harm your visibility there, and that breaking content into tiny chunks is not required¹.

Outside Google the evidence is thinner. SE Ranking found that 10.13 percent of the roughly 300,000 domains it studied had an llms.txt file, and that the file showed no measurable link with how often a domain was cited in major AI answers⁶.

So what genuinely differs from classic SEO?

Three things, and all three are practical rather than philosophical.

• Being quoted, not only ranked. A search results page is a list, and you can sit at position four. An AI answer names a few sources or brands and moves on. Google's rule for its own AI features is that a page must be indexed and snippet-eligible to be a supporting link². Other assistants set their own rules, so what one says about your brand can differ from what another says.
• Outside mentions weigh more. In Ahrefs' September 2026 data for US queries, the most-cited domains in ChatGPT were led by Reddit at 16.8 percent mention share and Wikipedia at 7.0 percent, followed by consumer-review and publisher sites⁴. Ahrefs measures that share against the top-cited sources, not against every citation. Commenters in one Hacker News thread said a product could be recommended for a week and then drop out unless outside mentions kept coming⁸. Treat that as an anecdote. Google, for its part, says seeking inauthentic mentions is not as helpful as it might seem¹.
• Crawler access is a separate gate for each assistant. OpenAI documents different crawlers for search, training and user-initiated visits⁵, and Google says crawling must be allowed in robots.txt and by any CDN or hosting layer². A site can be open to Google and shut to another assistant. See Is my website blocking ChatGPT and other AI crawlers?.

Which of the three do you actually need?

Start with sound SEO: pages that answer real buyer questions, are crawlable, and say plainly who you are and what you do. That base serves Google's AI features directly¹.

Then measure instead of guessing. A low-cost test is to write about 20 questions a real buyer would ask, put them to two or three AI tools, and log which brands appear, whether sources are cited and whether your business is described accurately. Treat the result as a sample, not a ranking, because answers vary with wording, model and context⁹.

Add GEO-style work only where the test shows a gap: facts that are wrong or missing, reviews and third-party pages that never mention you, or an assistant that cannot reach your site. That is a short list of fixes, not a separate discipline.