The SEO plugin on your website shows a row of green checkmarks and one red line: "No llms.txt file found." You've never heard of it.
Last week you asked ChatGPT who repairs furnaces in Columbus, and your company wasn't in the answer. Maybe the red line is why. Our guide to AI search for home service companies covers what does decide that.
What is an llms.txt file?
It's a short text file at yourdomain.com/llms.txt. It describes a site to AI tools, usually with a title, a brief summary and a list of main pages. Jeremy Howard proposed it in September 2024, and the proposal is at llmstxt.org.[1]
That page says it's used most for software documentation, where coding tools follow it to the right pages.[1]
What do Google, OpenAI and Bing say about it?
Google's guide to generative AI features lists llms.txt files among the things you can ignore, because Search itself doesn't use them.[2] It adds that making one for other services is fine and won't help or hurt your visibility in Google.[2]
Its page on AI features says the same about AI text files and markup.[3] Google's update log says it added the llms.txt note on June 15, 2026.[4]
Chrome's Lighthouse, a Google developer tool, has an experimental audit for AI agents that checks for the file. A missing file is marked not applicable, because it's optional for now.[5][6]
I searched OpenAI's help page on ChatGPT search and Bing's webmaster guidelines for llms.txt, and neither mentions it.[7][8] OpenAI's page says to let OAI-SearchBot crawl your site, and to check that your host lets OpenAI's published IP addresses through.[7] Bing's guidelines cover Copilot as well as Bing search.[8]
OpenAI publishes an llms.txt for its own developer docs, at developers.openai.com/llms.txt.[1] Its crawler page says nothing about ChatGPT reading yours.[9] The crawler pages Anthropic and Perplexity publish for site owners say nothing about their assistants reading yours either.[10][11]
Should you make one anyway?
If you want one, go ahead. It takes about half an hour, costs nothing, and Google says it won't hurt your Search results. Keep it to facts you'd put on a business card, and update it when your hours change.
I wouldn't pay for one, and I'd be wary of anyone who sells it as the reason an assistant will name you. None of the pages above says that.
A whole llms.txt file for a roofing company
- # Example Roofing Co.
- > Roof repair and replacement in Frisco, Texas and nearby towns.
- - Services: roof repair, roof replacement, roof inspections
- - Towns served: Frisco, Plano, McKinney, Little Elm
- - Phone: 214-555-0142
- - Hours: Monday to Saturday, 7 a.m. to 5 p.m.
- - Main pages: www.example.com/roof-repair, www.example.com/roof-replacement, www.example.com/contact
Illustrative example
The proposal's own format lists each page as a link with a few words after it, so a real file would write the last line that way.[1]
What should you do instead?
If the real question is why ChatGPT doesn't name you, read why it names competitors instead, then start where OpenAI's help page points: make sure its search crawler isn't blocked. The two-minute check shows how. If an answer gets your hours or phone number wrong, trace it to its source. For Google's side, read how to show up in Google AI Overviews. For a full plan, read how to get your business ready for AI search.
Our AI search visibility audit checks whether AI crawlers can reach your pages and whether your site says plainly what you do and where.
What I can't tell you
Only the companies themselves know what their assistants do with the file. A page that never mentions llms.txt doesn't prove an assistant ignores it. I can only report what their pages said on October 11, 2026.