Search engine optimization: a definition for AI search

99Visibility Research · Updated October 21, 2026 · 3 min read

Short answer

Search engine optimization (SEO) is the work of making web pages crawlable, indexable and relevant so search engines can find, store and show them for the right queries. It covers technical access, content that matches what people search for, and the controls that decide how a page appears. Google says the same foundations govern AI Overviews and AI Mode, with no additional technical requirements.

Key takeaways

SEO has three jobs: let crawlers fetch the page, get it into the index, and make it relevant to real queries.
Google states that a page must be indexed and snippet-eligible to appear in AI Overviews or AI Mode, and that there are no additional technical requirements.
Eligibility is not inclusion: Google says indexing and serving aren't guaranteed.
Other AI engines use their own crawlers, so per-bot access and server-rendered content matter beyond Google.
Schema, llms.txt, E-E-A-T scores and domain authority are not documented levers for AI answers.

What search engine optimization means

SEO is the practice of removing obstacles between a page and the people searching for what it offers. A search engine has to fetch the page, store it, and judge that it answers a query. SEO is the work at each of those steps.

The term predates AI search, but the definition hasn't changed. What has changed is the number of systems reading your site. Google, Bing, ChatGPT search, Perplexity and Claude each run their own crawlers or rely on an index someone else built.

How SEO works

SEO runs in three stages, and a failure at any one stops the rest.

Crawling. A bot requests the page. robots.txt rules, firewalls and CDNs decide whether it gets through. Rendering matters too: Googlebot executes JavaScript, but Vercel found that ChatGPT and Claude crawlers fetch JavaScript files without running them, so content that appears only after JavaScript runs can be invisible to them.
Indexing. The engine stores the page. A noindex tag or a canonical conflict keeps it out.
Serving. The engine matches the page to a query. Topical relevance does the work here. Snippet controls such as nosnippet and max-snippet decide how much of the page can be shown.

The next move: check each stage in order. A relevance problem can't be fixed while a crawler is still blocked.

Why SEO matters for AI visibility

Google is direct about this. Its AI features documentation says a page must be "indexed and eligible to be shown in Google Search with a snippet" to appear as a supporting link in AI Overviews or AI Mode, and adds: "There are no additional technical requirements." The same page notes that indexing and serving aren't guaranteed.

Ranking still correlates with citation, loosely. Ahrefs found in March 2026 that 37.9% of URLs cited in AI Overviews also appeared in the first 10 results. Most citations came from further down.

Outside Google, the access layer gets more specific. As of October 2026, OpenAI uses OAI-SearchBot for ChatGPT search and GPTBot for training, and the two settings are independent. Blocking the wrong one removes you from search answers. The steps for each engine are in how to prepare your website for AI search.

Common misconceptions

"AI search needs a separate optimization." Google says there are no special optimizations needed for AI Overviews or AI Mode.
"Add schema to get cited." Google says structured data isn't required for generative AI search. Ahrefs' matched test found AI Overview citations fell 4.6% after pages added it.
"Improve your E-E-A-T score." Google says E-E-A-T isn't a specific ranking factor. There is no score.
"Build domain authority." Domain Authority is a Moz metric. Google publishes no site-level authority score.
"Publish an llms.txt." Google Search ignores it, and no other engine documents reading it.
"Cover every long-tail variant." Google's AI optimization guide says you don't need to.

The evidence behind this is summarized in on-page rewrites vs access fixes.

Frequently asked questions

Is SEO the same as GEO?

They overlap heavily. For Google's AI surfaces, Google says standard SEO eligibility is the whole technical requirement. GEO adds the other engines, each with its own crawler and index, and the question of how AI describes your brand. Most claimed GEO techniques were measured in lab setups on content already inside the model's context, not on live search.

Does ranking in the top 10 get me into AI Overviews?

Not reliably. Ahrefs found in March 2026 that 37.9% of URLs cited in AI Overviews also appeared in the first 10 results, so most citations came from pages ranking lower. Ranking helps you get noticed, but nothing guarantees a citation. What you control is being indexed and snippet-eligible.

Does SEO cover ChatGPT and Perplexity?

Partly. The same principles apply: the crawler must reach the page, the content must be in the HTML, and the page must be relevant. The specifics differ. ChatGPT search depends on OAI-SearchBot, Perplexity on PerplexityBot. Check that robots.txt and your firewall let each one in. The free checker on this site shows whether ChatGPT names you for three buyer questions.

Sources

This page is AI-assisted. It was written from a verified evidence base and checked against our editorial policy. Engine behaviour changes often; facts are as of October 21, 2026.