llms.txt is a proposed plain-text file at the root of a site that tells machines which pages to read. Think of it as a polite map, not a lock and not a certificate.
What it is good for
Pointing a crawler at the pages that actually describe the company, instead of the tag archive and the popup stack. That is useful. It costs almost nothing.
What it cannot do
It cannot prove the site is yours. Anyone who controls the domain can write one. It cannot replace markup. It cannot stand in for a third-party file when the question is “who attested this.”
Use both: a hint on the domain, and a public record that is not the brochure. That pairing is llms.txt and verification.
Read why this exists. Check a name in the registry. Or start with a free check. Gold is $297/year for a fuller owner-managed identity with supporting sources.