Introduced as a proposal in 2024, llms.txt is conceptually similar to robots.txt or a sitemap, but aimed at AI: instead of controlling crawling, it offers a curated, Markdown-friendly map of your key pages and context, so a model ingesting your site can find the signal without wading through navigation and boilerplate.
It's important to be honest about status: major AI providers have not committed to reading llms.txt, so it isn't a guaranteed channel today. Treat it as low-cost, forward-looking hygiene — easy to add, potentially useful as standards mature — rather than a core tactic.
It does not replace the fundamentals of GEO: crawlable content, clear structure, structured data and authority still do the heavy lifting for AI visibility. llms.txt is a small, optional addition on top.