max-snippet
max-snippet is a robots meta rule that limits how many characters of your page Google may quote, in search results and in AI Overviews and AI Mode.
max-snippet is a rule you add to a page to limit how many characters of its text Google may show as a snippet. It goes in a robots meta tag, like <meta name="robots" content="max-snippet:50">, or in an HTTP header. Google says the limit also applies to how much of the page may be used as direct input for AI Overviews and AI Mode.
With nosnippet you stop quoting altogether. With max-snippet you choose how much.
The values
max-snippet: followed by a number caps the snippet at that many characters. max-snippet:0 means no snippet at all, the same as nosnippet. max-snippet:-1 lets Google choose the length, which is what happens if you set nothing.
You can find the full list of rules in Google's documentation on the robots meta tag. There's also data-nosnippet, an attribute you put on part of a page to keep just that part out of snippets.
When to use it
Most brands want their pages quoted, so most shouldn't set it. It's for publishers whose content is the product, like a recipe site or a paid newsletter, who want to show enough to be found without giving the whole thing away.
For example, a coffee magazine might set max-snippet:160 on its reviews. Google can still show a line or two and use a little in an AI answer, but not the full tasting notes.
Be careful with it. A tight limit on your pricing or product pages can mean Google uses less of your own words in its AI answers, and more from other people's pages about you.
How it differs from robots.txt
robots.txt decides whether a bot may read a page at all. max-snippet lets Google read the page and limits how much of it can be shown or used. It's a Google rule, so check each platform's own documentation before you expect others to follow it.