llms.txt is meant to make websites easier for agents to read. Instead of HTML with navigation and scripts, they get a short description and a link list, ideally pointing to Markdown versions of the pages.
According to the proposal, only an H1 with the name of the site is required. Optionally it is followed by a blockquote summary, explanatory paragraphs, H2 sections with link lists and an “Optional” section for links that can be skipped. The file can also sit in a subpath such as /docs/llms.txt.
Google Search does not use llms.txt, as Google states in its guide to generative AI features. An SE Ranking analysis of almost 300,000 domains found no link to AI citations. The file is most common on developer documentation sites. More in our article llms.txt: what the file does.