What is an llms.txt file and do I need one?

llms.txt is a proposed convention: a plain-text file at your site root that points AI systems at your most useful content:

• It is a convention, not a standard - no search engine requires it and Google has said it does not use it.
• Adoption is early but rising - 27% of Australian small business sites publish one, up from 19% a quarter earlier^*.
• It costs almost nothing - a short file listing your key pages, if you want to place the bet.

Treat it as optional. Clear, well-structured pages do far more for AI visibility than any single file.