AIO, AEO, GEO, and LLMO all refer to optimizing so that AI search uses your site. AIO (AI Optimization) is the umbrella term, with AEO (being chosen as the answer), GEO (being cited by generative AI), and LLMO (being correctly understood by language models) underneath it. The four are not competing methods — they differ in which audience they address and at which stage. So "which one to do" is not a matter of preference; it is decided by the stage your site is currently at.
How the Four Terms Relate
The four are not parallel options. AIO is the umbrella, with AEO, GEO, and LLMO underneath. What separates them is which audience you are trying to be read by.
| Term | Audience | In one line |
|---|---|---|
| AIOAI Optimization | AI search in general | The umbrella term covering the other three — the whole effort of adapting to AI search |
| AEOAnswer Engine Optimization | AI Overview and answer engines | Aims to be chosen as the answer to a question. Direct answers and FAQ structure are central |
| GEOGenerative Engine Optimization | ChatGPT, Gemini, Perplexity, etc. | Aims to be cited as source material when generative AI assembles an answer |
| LLMOLarge Language Model Optimization | The language models themselves | Shapes pages so models do not misread their structure and meaning. The most technical layer |
Note that these terms are not defined consistently across the industry — expect the boundaries to shift depending on the author. This article uses the classification above throughout.
What Each Term Means, and Common Misconceptions
What is AIO?
AIO (AI Optimization) is the umbrella term for the whole effort of getting your site used by AI search. It is not the name of a specific technique — it groups AEO, GEO, and LLMO together. Depending on context, AIO is also used to refer to Google's AI Overview itself, and this double usage is a common source of confusion.
Common misconception: There is no standalone menu of work called "AIO optimization." Because it is an umbrella term, it breaks down into the three below — or into plain SEO — the moment you start doing actual work.
What is AEO?
AEO (Answer Engine Optimization) aims to get your content chosen as the answer to a question. It targets systems that return an answer rather than a list of links, such as Google's AI Overview and voice assistants. Question-and-answer pairings, stating the conclusion up front, and FAQ-style headings tend to work well here.
Common misconception: Adding FAQ structured data does not by itself get you selected as the answer. Structure helps AI avoid misreading your content; it is not the reason you get chosen.
What is GEO?
GEO (Generative Engine Optimization) aims to have your content cited or referenced as source material when generative AI such as ChatGPT or Gemini assembles an answer. Where AEO looks at being displayed as the answer, GEO looks at being referenced while the answer is being built. Primary information, concrete numbers, and explicit sourcing tend to be rewarded.
Common misconception: This is different from GEO as an abbreviation for local/geographic SEO. The two are easy to confuse when searching, so check the context.
What is LLMO?
LLMO (Large Language Model Optimization) is the most technical layer: shaping pages so models do not misread their structure and meaning. It covers logical heading hierarchy, having the body text actually present in the HTML, guidance via llms.txt, and whether crawlers can physically reach the page. It helps to think of it as improving machine reading accuracy rather than human readability.
Common misconception: Publishing llms.txt does not finish the job. If your body text only renders via JavaScript and is not present in machine-readable HTML, a guidance file alone will not get your content read.
If you want to go deeper on the definitions themselves, our sister site covers each term's background and comparisons in AIO, AEO, GEO, and LLMO explained. This article leans toward deciding what to tackle first from where your site stands, rather than exhaustively defining the terms.
The Shared Foundation Is SEO Itself
Danny Sullivan, who leads search liaison at Google, has said in effect that SEO for AI is just SEO. AI search is certainly a new mechanism, but the judgment of what to select as a source sits on the same continuum as the evaluation traditional search has built up.
Ahrefs research reports that roughly 60% of AI Overview citations come from the top 10 organic results. Conversely, about 40% are cited from outside the top 10, so rankings are not everything. Still, the figure shows that the conditions for ranking and the conditions for being cited overlap heavily.
Rankings and backlinks are outcomes. What determines whether you get cited in AI search is the layer producing those outcomes — whether the page is machine-readable, and whether it is shaped like an answer to the intent. All four terms sit on this same foundation.
Which to Tackle First — Decide by Your Current Stage
You do not need to pursue all four at once. The order that produces results is determined by the state your site is in right now.
Put the AI search discussion on hold
AI Overview and generative AI mostly draw on Google's search index. A page that is not indexed is not even a candidate for AI search. Fix the basics first — titles, meta descriptions, heading hierarchy, internal links. If you have time to research terminology differences, spending it here will produce results faster.
Lean toward AEO
Put a one- or two-sentence direct answer to the search intent at the top, organize key points as bullets, and build question-and-answer pairings. Implement Article and FAQPage structured data so AI does not misread the content. At this stage the content is usually being read but is not yet shaped like an answer.
Move on to GEO and LLMO
Check whether AI crawlers can actually reach the page, whether the body text exists in the HTML, and whether llms.txt provides guidance. Strengthen the E-E-A-T foundation with author information, operator information, and original data. From here the work becomes a medium-to-long-term effort to build reasons to keep being cited.
If you are at Stage 2, our practical guide to AIO optimization walks through direct answers, structured data, heading structure, and E-E-A-T as a prioritized sequence. This article decides which to do; that one covers how to do it.
How to Measure Where Your Site Stands
Judge the stage by measurement, not by feel. Working through the following in order determines your stage mechanically.
Measure whether you are indexed
Use URL Inspection in Google Search Console. Anything other than "indexed" — for example "Crawled - currently not indexed" — puts you at Stage 1. Skipping this and moving on to later work will not help.
Measure whether AI crawlers can reach you
Rendering in a browser and being readable by an AI crawler are different things. Even when robots.txt allows it, a WAF or bot protection may be blocking access. Direbase's AIO readiness check actually requests your page under the same conditions and reports whether it got through.
Measure the foundations
Check structured data, heading hierarchy, meta tags, and internal links in one pass. Stages 1 and 2 need almost nothing outside this range — it is the part to fix before doing anything special for AI search.
Measure whether you are being cited (current limits)
No official tool currently aggregates AI search citations directly. Google Search Console has no filter that isolates AI Overview either. For now, the most reliable method is to search your target queries yourself and visually confirm whether your site appears in the AI Overview or the generative AI answer.
Measure It Now
Enter a URL to audit structured data, basic SEO, content, and technical SEO. This covers in one pass what Stages 1 and 2 require.
Check AI Crawler Reachability
Before moving to Stage 3, confirm that AI crawlers can actually reach your site. Being visible in a browser and being readable by a machine are different things.
Open the AIO readiness checkCommon Mistakes
Organizing the terminology becomes the goal
AIO, AEO, GEO, and LLMO are not defined consistently across the industry — the boundaries shift depending on who is writing. Continuing to research in search of a precise line does not change the state of your site. Use the terms as labels for which audience you are addressing, and switch to judging your current stage when it is time to act.
Treating llms.txt as the finish line
llms.txt is a guidance file for AI crawlers, not a guarantee that your content gets read. If the body text is not present in the HTML, or crawlers are being blocked, the guidance points at nothing. Publishing it is worthwhile, but reachability and body-text presence come first.
Budgeting AI search work separately from SEO
Google's Danny Sullivan has said, in effect, that SEO for AI is just SEO. Ahrefs research also found that roughly 60% of AI Overview citations come from the top 10 organic results. Since the foundation is shared, splitting them into separate initiatives means estimating the same work twice.
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FAQ
What is the difference between AIO, AEO, GEO, and LLMO in one line?▾
Which of the four should I tackle first?▾
Should AI search work have a separate budget from SEO?▾
Does publishing llms.txt complete my AI search optimization?▾
Is GEO the same as local SEO?▾
Start by Confirming Your Stage
Sorting out the terminology does not change the state of your site. Enter a URL and settle which stage you are at first.
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Written by
今井政和SEO Director / Frontend Developer
SEO Director with 20+ years of web industry experience. Creator of Direbase and the official WordPress plugin "ORECTIC SEO CHECK." Author of a book on web strategy inspired by Edo-era merchant principles.
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