How does generative engine optimisation work?

A generative engine searches, reads a few pages, then writes one answer

A generative engine finds pages through search, reads a handful of them, and writes a single answer with links to its sources. A generative engine is a search tool that writes an answer instead of showing a list of links. ChatGPT search, Perplexity, Gemini, Google AI Overviews and Google AI Mode all work this way.

The name GEO comes from a 2023 paper by researchers at Princeton University and IIT Delhi (Aggarwal et al., KDD 2024). They used it for the work of getting a page used in these answers. Our generative engine optimisation page covers what the work involves. This guide explains the mechanism underneath it.

Each answer is built in four steps

Each answer goes through four steps: plan the searches, fetch the pages, write the reply, and link the sources. The details differ between engines, and each engine publishes only part of how it works. What they do publish fits this order.

The question becomes several searches

Google says AI Overviews and AI Mode may use a "query fan-out" technique (Google Search Central). Query fan-out means the engine runs several related searches on parts of the question to find supporting pages. A question such as "Is a home battery worth it in Sydney?" might become separate searches on battery prices, rebates and payback times.

The engine fetches pages from a search index

A search index is the store of pages that a search engine has collected and saved. A crawler is the program that visits pages to collect them. Google's AI features draw on Google's own index. ChatGPT search relies on OpenAI's crawler, OAI-SearchBot (OpenAI). Perplexity uses PerplexityBot (Perplexity), and Claude uses Claude-SearchBot (Anthropic). A page that the crawler never collected cannot be fetched for an answer.

The model reads the pages and writes

A language model is the part of the engine that writes. It reads the pages it fetched, takes the passages that answer the question, and combines them into one reply. A passage that states the answer plainly is easier to use than one that hides it under a page of history.

The answer links the pages it relied on

Most engines show links to the pages behind an answer. Google says AI Mode responses come with links to supporting websites. A citation is one of those links. A mention is when the answer names your business in its text. You can get one without the other, so it pays to track both.

GEO changes what happens at each step

GEO works on all four steps. Your site needs to be reachable, retrievable, quotable and corroborated.

Be reachable

Reachable means the engine's crawler is allowed to visit your pages. Your robots.txt file controls this. Robots.txt is a text file at the root of a site that tells crawlers which pages they may visit. OpenAI says sites that opt out of OAI-SearchBot will not be shown in ChatGPT search answers. Blocking GPTBot, its training crawler, is a separate choice.

Few businesses get this wrong. We checked 1112 Australian business websites across 34 locations in October 2026, and 2% blocked an AI search crawler. The method is on our local data page. The check takes five minutes, so do it anyway.

Be retrievable

Retrievable means your page is indexed and ranks for the searches the engine runs. This part is ordinary SEO. Google says a page must be indexed and eligible to show with a snippet. It also says there are no additional requirements to appear in AI Overviews or AI Mode. Because of query fan-out, the searches that count include the smaller questions as well as the main one. A page that answers "how much does it cost" can be fetched for a question that never uses those words.

Be quotable

Quotable means the page gives the model sentences it can lift. Put the answer in the first two sentences, then support it with facts, figures and named sources. The GEO paper tested nine ways of rewriting a page against a benchmark of questions. Adding quotations, adding statistics and citing sources did best, with gains of up to 40% on the paper's main measure. Keyword stuffing did worse than leaving the page alone.

Our guide on what the GEO research found covers the results and their limits. Our guide to writing pages that get quoted shows how to structure a service page.

Be corroborated

Corroborated means other sources agree with what your site says. Keep your business name, address, phone number and services the same on your site, your Google Business Profile and the directories that list you. When sources agree, an engine can connect them to one business.

Structured data helps with this. Structured data is code on a page that states facts, such as the business type and address, in a fixed format. In the same check, only 29% of sites had LocalBusiness structured data. Our LocalBusiness structured data guide shows how to add it. Google says its AI features need no special markup, so treat structured data as a way to remove guesswork.

The same question can get a different answer each time

Generative answers change from one ask to the next and from one engine to another. The model writes each reply fresh, so asking twice can give different wording and different links. Google says AI Overviews and AI Mode may use different models and techniques, so their responses and links can differ. Each engine also has its own crawler and index, so a page that one engine has collected may be missing from another.

For measuring, this means a single check proves little. Ask the same questions several times on several engines, then count how often you are named and how often your site is cited. Our own data pipeline does this with Gemini and Google Search grounding. It asks local questions such as "Who are the best plumbers in [suburb]?" several times and records which businesses are named and which sites are cited. Our guide to checking AI mentions sets out a version you can run yourself.

Start with crawler access and work forward

Work through the steps in the order the engine does. Each one depends on the step before it.

1. Open yoursite.com.au/robots.txt and check that it does not block Googlebot, OAI-SearchBot, PerplexityBot or Claude-SearchBot.
2. Check in Google Search Console that your main pages are indexed. Search Console is Google's free tool that shows which pages it has indexed and which searches they appear for.
3. Rewrite the opening of each service page so the first two sentences answer the question a customer asks.
4. Add facts a model can quote: areas served, typical timeframes, qualifications and any figures you are happy to publish.
5. Make your business details match everywhere, then add LocalBusiness structured data.
6. Set up a monthly check of what the main engines say about your category in your area.

None of these steps guarantees that an engine will name you. Each one removes a reason for it to leave you out.