In 1620 Francis Bacon listed the ways the human mind fools itself. He called one group the idols of the market, the errors that come from people talking to each other. Words, he warned, can name things that do not exist.
Search marketing coins new words quickly: GEO, AEO, "AI visibility", and now a plain text file called llms.txt. Before you add the file to your site, it helps to ask what it does and who reads it. Google has answered that question in writing and updated its answer twice in 2026, so some articles you will find predate it.
What llms.txt is
llms.txt is a proposal, not a standard. Jeremy Howard published it on 3 September 2024 as a way to give AI agents a short, curated guide to a website. The file lives at /llms.txt and is written in Markdown. It has one required part, an H1 with the site or project name. After that come an optional summary and sections of links to the pages that matter, each with a short note, plus an "Optional" section for links an agent can skip.
Think of it as a table of contents written for a machine. It is not a robots.txt file. It does not block or allow anything.
What Google has said
Here is the record, oldest first. We opened each source on 19 October 2026.
| Date | Who | What was said |
|---|---|---|
| 3 Sep 2024 | Jeremy Howard | Proposed the /llms.txt file for AI agents. |
| 17 Jun 2025 | John Mueller, Google | On Bluesky, as reported by Search Engine Roundtable: "FWIW no AI system currently uses llms.txt." |
| 15 May 2026 | Added a guide on optimizing for generative AI features in Search. | |
| 20 May 2026 | Search Engine Journal | Reported that Google's guide lists llms.txt among the tactics you do not need for generative AI features, and that Mueller compared the file to the keywords meta tag. |
| 15 Jun 2026 | Search updates changelog: "Added a note to the AI optimization guide clarifying Google Search's usage of llms.txt files." |
Google's AI optimization guide is the primary source. It says: "You don't need to create new machine readable files, AI text files, markup, or Markdown to appear in Google Search." It also says Google Search does not use these files, and that making one for other services is fine and will neither harm nor help your visibility in Google Search. The page we read was last updated on 10 July 2026.
The same guide treats the new labels with some suspicion. It says "AEO" and "GEO" describe improving visibility in AI search, which is "optimizing for the search experience, and thus still SEO". It also says many suggested "hacks" are not effective or supported by how Google Search works. Bacon would have recognized the move: a new name makes a practice sound like a new discipline.
What about other AI systems
Google is one reader. The file was proposed for AI agents in general, so it is fair to ask about the rest.
- Chatbots and AI search: Mueller's June 2025 post says no AI system uses the file. We found no public statement from another AI company saying its search or chat product reads llms.txt to decide what to cite. Absence of a statement is not proof, so treat this as "unconfirmed", not "never".
- Browser agents: Chrome's Lighthouse 13.3 added an experimental Agentic Browsing category with an llms.txt audit, according to Search Engine Journal. That audit is about readiness for browser agents. It is separate from SEO and says nothing about rankings or citations.
- Developer documentation: this is where the file has a real home. Anthropic publishes one for its API docs: a Markdown index of its English documentation pages, each linked to a Markdown version. A coding assistant that is already reading those docs can use a clean list of pages. Whether it does so for any given product is up to the product.
The pattern is consistent. The file may help an agent that already decided to visit your site. Nothing public shows it makes an AI system choose your site.
Should you add one
- For Google Search and AI Overviews: no. Google says it ignores the file. Adding it will not hurt, and it will not help.
- If you run developer docs or a help center that agents read: it is cheap and reasonable, and Google says it is fine. Keep it small, accurate and in sync with the pages it lists.
- If you hope it will make ChatGPT, Perplexity or Gemini cite you: there is no public evidence for that. Do not pay anyone for it, and be wary of tools that promise it.
What to do for AI search instead
Google's guide points to the basics instead of new files. Its AI features page says there are "no additional requirements" to appear in AI Overviews or AI Mode, and that no special schema.org markup is needed. In practice that means:
- Make sure Googlebot can crawl and index the page. Check this in Search Console.
- Link to the page from other pages on your own site.
- Publish original content that helps a person. Google's guide warns that seeking inauthentic mentions across the web is less helpful than it seems.
- Keep any structured data you use consistent with the visible text on the page.
- Treat any tool that sells "AI ranking" access with care. Google's guide says no third-party tool has access to its internal ranking or AI systems.
For the wider picture of how the terms relate, read our post on SEO, GEO and SEM. If you are weighing a bigger SEO decision first, our post on whether domain age is a ranking factor shows the same method: read what Google actually said, then decide.
Frequently asked questions
Does llms.txt help SEO?
Not for Google Search. Google's guide says Google Search does not use these files and that having one will neither help nor harm your visibility there.
Does llms.txt help me get cited by ChatGPT or Perplexity?
We found no public confirmation from those companies that they read the file to choose sources. Mueller said in June 2025 that no AI system currently uses it. Treat any claim of a citation boost as unproven.
Can llms.txt hurt my site?
Google says maintaining one will not harm your visibility or rankings in Google Search. A stale file that lists pages you have removed could mislead an agent that does read it, so keep it accurate.
Is llms.txt the same as robots.txt?
No. robots.txt tells crawlers what they may fetch. llms.txt is a suggested reading list for AI agents and blocks nothing.
Should I add llms.txt if I have developer docs?
It is a reasonable, low-cost choice, and Anthropic does it for its own API docs. Do it for the readers who use it, not for rankings.