What an llms.txt File Is, Why It Matters, and What to Put in It

An llms.txt file is a plain-text, prose summary of a website written for language models rather than traditional search crawlers, based on a proposal published by Jeremy Howard in September 2024. No major AI company has confirmed it reads the file, but the author argues it is still worth creating because the process forces businesses to articulate clearly what they do, who they serve, and what they refuse to claim. The file sits alongside robots.txt, sitemap.xml, and schema markup, but is unique in using natural language to convey context that structured data formats cannot capture. Effective entries should include a one-sentence summary that stands alone, a clear boundary of services, a description of the intended buyer, and correctly spelled name variants. The core argument is that the clarity required to write the file well tends to improve the broader website, making the exercise valuable regardless of whether AI systems ever act on it.