llms.txt: A Proposed Standard No Major AI Platform Has Confirmed It Uses

Despite widespread discussion, llms.txt—a proposed Markdown file for guiding AI crawlers—remains unsupported by major AI platforms. 2026 data shows only 10% adoption, negligible crawler requests, and explicit rejection from Google. Yet the article argues it's still worth publishing: it's cheap, forces content audits, and serves as a business-to-agent surface. Includes practical tips for writing and testing llms.txt.