Google Webmaster Guidelines
Google Webmaster Guidelines were Google's rules for getting a site into its results. They're now called Google Search Essentials.
Google Webmaster Guidelines were Google's published rules for sites that want to appear in its search results: what Google needs to find and index your pages, what it treats as spam, and what helps you do well. Google has since renamed them Google Search Essentials, so when someone mentions the Webmaster Guidelines, that's the page to read.
They matter because breaking them is how sites lose their place in Google, and now in Google's AI answers too.
What's in Search Essentials
Google splits it into three parts. The technical requirements are the basics Google needs to show a page at all, and most sites meet them without trying. The spam policies list the tactics that can get a page ranked lower or removed, such as cloaking, doorway pages, keyword stuffing and link spam. The key best practices cover helpful content written for people, using the words people search with in your titles and headings, crawlable links, and structured data.
Google is also clear that appearing in its results is free, whatever anyone tries to sell you.
The guidelines and AI answers
Google says there are no extra requirements for its AI Overviews and AI Mode. A page needs to be indexed and eligible to appear in Search with a snippet, and the usual SEO best practices apply. So for Google's AI answers, Search Essentials are the rules to follow.
For example, if Kestrel Roasters' product pages carry a noindex tag left over from a redesign, they drop out of Google's results, and so out of the links in Google's AI answers too.