The AEO Guide, 2026 edition · Part one, Understand
02

Chapter two of ten

How answer engines work

An engine answers from memory or through retrieval, a live search of the web. Retrieval is the part you can shape.

Buyers ask Does ChatGPT already know us, or does it look us up?

By Maeva Cifuentes · Updated October 2026

Read this chapter as

The short answer

An answer engine has a memory and a browser. Models build a memory from their training data. The labs refresh that data every few months, which puts it outside our real-time influence. Retrieval is the live search the engine runs before it answers. It drives buying questions and it responds to work you can do this quarter, so this guide focuses on retrieval.

Memory and retrieval

Maybe you have seen this before. An engine quotes your page as a source and then recommends three competitors. Or it names you on Monday and leaves you out on Tuesday. Both come from how the engine builds an answer.

Picture a well-read expert with a browser. For some questions the expert answers from what they already know. That is training data, which the model absorbed months ago and which stays frozen until the next model ships.

For other questions the expert opens the browser, reads a handful of pages and then answers. That is retrieval, the term this guide uses for an engine's live search. Google's own developer documentation says the model decides for itself whether a search would improve the answer.

How often the engine reaches for sources

A model that thinks harder retrieves more

100 buyer-journey prompts run twice through GPT-5.2. Source Growth Memo, Reasoning lift, using Semrush data. A separate academic study of logged conversations found GPT-4o answering about 24% of prompts with zero site visits, against about 2% for Perplexity's model (Strauss et al.).

Try it

Memory or retrieval

Pick a question a buyer might ask and see how an engine tends to handle it.

Memory
Retrieval

Typical behavior drawn from the studies cited in this chapter. Engines and settings vary.

If you decide

Buying questions tend to trigger retrieval, so the money you spend on being findable and well described pays back where buyers choose.

If you do the work

Ask your buyers' questions with web search turned off, then on. The difference shows what the model remembers and what it finds.

What happens during retrieval

A brand can drop out at any of retrieval's four steps.

  1. 1

    It decides to retrieve

    Fresh, specific and commercial questions push the engine toward the browser.

  2. 2

    It splits the question

    One prompt becomes several smaller searches. Google calls this query fan-out.

  3. 3

    It collects pages

    Each search returns a set of pages from the engine's index.

  4. 4

    It picks and writes

    The engine retrieves far more pages than it cites, then writes one answer.

In The Search Spot study of 488 product pages, ChatGPT ran a category search first and then searched for vendors by name. Pages ranking in Google's top 10 for five or more searches were cited regularly 76% of the time, against 10% for pages below that mark. Brands that rank in the top 10 for a wider set of relevant keywords are far more likely to be cited.

Chapter 3 goes deep on the splitting step and how to see the searches an engine runs for your category.

4.6x

more searches with high reasoning than with minimal, 1,130 against 245 across 100 prompts

Growth Memo with Semrush
6.7x

more pages retrieved by ChatGPT than cited. 85% of retrieved pages go uncited.

AirOps, 548,534 retrieved pages
10 → 5

median pages Perplexity's model visited and then cited per answer

Strauss et al., 2025

Step four, picking

The page the engine finds first gets cited far more often

Share of retrieved pages that ChatGPT cited, by position in its search results. Source Growth Memo with AirOps, 815,484 query and page pairs. Bar charts in this chapter share one scale from 0 to 100%.

If you decide

Being cited and being mentioned are separate wins. Ask your team which step the brand is dropping out at before funding more content.

If you do the work

Check each step in order. Confirm the bots can reach the page, confirm it ranks for the smaller searches, then look at what the page says.

Cited and mentioned, defined

Important definitions for you to understand

Cited

  • What it meansThe engine retrieved one of your pages and lists it as a source for the answer, usually as a link or a numbered reference.
  • What it tells youYour page was found and used. A citation is about a page.

Mentioned

  • What it meansThe engine names your brand in the text of the answer, as an option or a recommendation.
  • What it tells youThe buyer saw your name. A mention is about a brand.

One answer, two outcomes

Here your page is cited and your brand goes unmentioned. The reverse also happens, where an engine names you from memory and links to someone else's page.

We treat mentions as the main goal and citations as the path to them. Chapter 8, on measurement, shows how to track each one.

If you decide

Ask for both numbers in every report. A high citation count with few mentions means the engines use your content to recommend someone else.

If you do the work

Log cited pages and mentioned brands as separate columns for each prompt, so the two trends stay readable.

What you can influence

Both memory and retrieval shape an answer. We focus on retrieval, because it responds to work within weeks and it carries the buying questions.

Within your reach

  • AccessWhether the engines' bots can crawl and read your pages.
  • RankingsWhether your pages show up for the smaller searches an engine runs.
  • Your own wordsPlain facts on what the product is, what it costs and who it suits.
  • Other people's wordsWhat review sites, comparison lists, press and communities say about you.
  • FreshnessHow recently your key pages were updated.

Outside your reach

  • What the model already learnedTraining stays frozen until the next model ships. The lab alone chooses what goes in.
  • The decision to retrieveThe engine makes that call on each question.
  • The buyer's settingsModel, reasoning mode and plan all change the answer.
  • PersonalizationGoogle is feeding a person's history into Gemini and AI Mode.
  • The diceEvery answer carries some built-in randomness.

The two lists connect. What the web says about you today is what a future model learns from, so retrieval work done now becomes memory later.

Rankings carry a lot of the load. AirOps found that 43.2% of pages ranking first on Google were cited by ChatGPT, 3.5 times the rate of pages beyond the top 20.

If you decide

Fund the left-hand list and judge the team on it. Treat the right-hand list as weather, worth watching and pointless to fight.

If you do the work

Turn the left-hand list into your audit. Each line maps to a later chapter, from technical access to off-site mentions.

The engines side by side

The engines share the same four steps and differ in where they search and how much they show. Treat each one as its own channel.

ChatGPTGoogle AI Overviews and AI ModeGemini appPerplexity
Where it retrieves fromThird-party search providers plus content from partners. April 2025 court testimony named Bing and described OpenAI's own index as still in development.Google's search index, with several related searches per question.Google Search, when the model judges a search useful.Its own search index.
Bots that feed retrievalOAI-SearchBot builds the index. ChatGPT-User fetches a page live.Googlebot.Googlebot.PerplexityBot builds the index. Perplexity-User fetches a page live.
Bot that feeds trainingGPTBot.Controlled through Google-Extended.Controlled through Google-Extended.Perplexity says its bots stay out of model training.
What a page needsOAI-SearchBot allowed in robots.txt. Blocked sites drop out of search answers.Indexed and eligible for a snippet. Google asks for zero special files or markup.The same as Google Search, with Google-Extended allowed, since that token also controls grounding in Gemini Apps.PerplexityBot allowed in robots.txt.
How it shows sourcesCited a source in about three of four logged answers.Links sit beside the answer and count in Search Console under Web.Left 92% of logged answers without a citation.Visited a median of 10 pages and cited 5.
What to watchHard questions get routed to a thinking mode that searches far more.AI Mode works as a closed loop where buyers accept the shortlist.Personal history shapes the answer.It searches on nearly every question.

Bot roles come from OpenAI, Google and Perplexity documentation. Citation figures come from Strauss et al., who studied about 14,000 logged conversations with GPT-4o, Gemini and Perplexity's Sonar in March and April 2025. Consumer apps may behave differently. The authors also note that OpenAI's logs look trimmed.

If you decide

Ask which engines your buyers use before spreading effort across all of them. Chapter 1 showed that 91% of cited pages appear in one engine only.

If you do the work

Open robots.txt and check the search bots by name. A training block on GPTBot leaves search untouched, while a block on OAI-SearchBot removes you from answers.

Why answers change

Ask the same question twice and you can get two different shortlists. Rand Fishkin of SparkToro and Patrick O'Donnell of Gumshoe had about 600 volunteers run 12 prompts close to 3,000 times. The chance of ChatGPT or Google returning the same list of brands twice came in under 1 in 100, and the same list in the same order came in near 1 in 1,000.

A trend still shows through the variation. That trend is what we measure. Three things cause the variation.

  • The dice

    A model picks its words with a little randomness built in, so each answer is one draw from many possible answers.

  • Different searches

    The engine may split the question differently each time and so read different pages.

  • A different asker

    Reasoning mode, location and personal history all shift the result.

  • What it means for you

    One answer is a sample. Track a category or theme of prompts and read the direction of your share across many runs.

The trend under the noise

The same brands kept appearing across 142 different wordings of one need

Volunteers each wrote their own prompt for buying headphones, and almost none resembled another. The 994 answers still named Bose, Sony, Sennheiser and Apple in 55% to 77% of cases. A broader B2B category showed lower shares, at 30% to 40% for the top brands. Source SparkToro with Gumshoe, January 2026. The author flags a small sample and a short time window.

That is why we track prompts at the level of a category or theme. Buyers phrase things in endless ways, so a single prompt tells you little, while a group of prompts on one theme shows which way you are moving.

How consistently ChatGPT cites the pages it retrieves

Never cited, 58%Cited some of the time, 17%Cited every time, 25%

Source Growth Memo with AirOps, 16,851 queries run three times each through the ChatGPT interface, with each page scored on how often it was cited across every query where it appeared. Segments share one scale from 0 to 100%.

Reasoning mode moves the result further. In the Growth Memo test, only 25.6% of cited domains appeared under both minimal and high reasoning.

If you decide

A screenshot of one answer proves little, whether it flatters you or alarms you. Ask for the trend by category or theme across a fixed set of prompts.

If you do the work

Group prompts by theme and report the direction of each group. Chapter 8 covers how tracking tools turn repeated runs into a share.

Other views

  • Retrieval is the whole game

    Ethan Smith of Graphite says AEO works on retrieval, since training data is hard to influence. We agree on where to focus.

  • Memory still tilts the pick

    Kevin Indig argues that what a model learned about a brand in training colors which retrieved pages it chooses to cite.

  • Personalization changes tracking

    Eli Schwartz expects personalization to spread from Gemini to AI Mode, then to AI Overviews and the rest of Google Search, so two people asking the same thing get different answers. We read that as one more reason to track themes over single prompts.

  • Nothing special required

    Google's documentation says pages need zero extra optimization to appear in AI Overviews or AI Mode.

Choose your next stop

Where to go from here

Sources