When Jeremy Howard proposed llms.txt in late 2024, most SEOs ignored it. Eighteen months later it's the single highest-leverage file you can add to a site for AI search visibility — and the engines have quietly started using it.
What llms.txt actually does
It's a markdown manifest at the root of your domain that tells AI crawlers, in their preferred format, what your site is about and where the canonical sources for each topic live. Think of it as a sitemap.xml written for language models instead of search bots.
The structure that works
- H1 with the brand name and one-sentence positioning.
- Blockquote with a longer description that includes your top three entities.
- Section headers grouping URLs by intent (Services, Case studies, Essays, Contact).
- Each link followed by a one-line description an LLM can use as anchor text.
What I'm seeing in client analytics
Sites that shipped a clean llms.txt in Q1 2026 are seeing a measurable lift in cited-source impressions across Perplexity and ChatGPT's web search. The lift is small in absolute terms but consistent — and the cost of shipping the file is roughly zero.
If you have a sitemap.xml, you have time to write an llms.txt.
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