llms.txt
llms.txt is a proposed Markdown file (like robots.txt) that gives AI models a curated map of your site's most important content.
Why it matters: no major engine has confirmed using it for citations yet, so treat it as low-cost future-proofing rather than a ranking lever.
Adopted by companies such as Anthropic, Stripe, and Vercel, it lists key pages and summaries in a machine-readable form.