nosnippet
nosnippet tells Google not to show text from a page in its results, and not to use the page as direct input for AI Overviews and AI Mode.
nosnippet is a rule that tells Google not to show any text from a page in its search results. You add it to the page as a robots meta tag, <meta name="robots" content="nosnippet">, or send it in the HTTP header. The page can still rank, but it shows up as a title and a link, with no description under it.
For AI search, nosnippet is the rule that controls how Google's AI features use your page. Google's robots meta tag documentation says it also stops the content from being used as direct input for AI Overviews and AI Mode.
Setting a limit with max-snippet
nosnippet is all or nothing. max-snippet sets a limit instead: the most characters Google may show from the page. Google says that limit applies to AI Overviews and AI Mode too.
You can also mark part of a page with the data-nosnippet attribute, so Google leaves that part out of snippets and keeps using the rest.
Think before you use it
Keeping your text out of AI Overviews sounds like protection, but it has a cost. If Google can't use your page as input, the overview is written from other pages, and those pages are the ones it links to.
For example, say Fernhill Coffee puts nosnippet on its brewing guides, worried that AI Overviews will answer the question and nobody will click. The overviews keep appearing for those searches. They're now written from Kestrel Roasters' guides, and they link to Kestrel.
There are good reasons to use it, like paid content or pages with text you're not allowed to republish. For pages you want customers to find, it usually works against you.
Other platforms
nosnippet is a Google rule. Other search engines and AI companies decide for themselves whether to follow it, so check their own documentation. To control what an AI company's bots can read in the first place, use robots.txt.