What Is an llms.txt File, and Does Your Business Need One?

What does an llms.txt file actually look like?

A valid file is short. Here is the shape of one:

# Ace Plumbing

> Licensed plumbers serving the Sacramento area since 1998.

## Services
- [Drain cleaning](https://example.com/services/drain-cleaning)
- [Water heater repair](https://example.com/services/water-heaters)
- [Emergency plumbing](https://example.com/services/emergency)

## About
- [Our team and licensing](https://example.com/about)
- [Service areas](https://example.com/service-areas)

That is genuinely all it needs to be. The heading names the business, the links point at pages that exist, and each link says plainly what it is. No marketing language, no keyword stuffing — an AI reader is not scoring you on enthusiasm.

What makes an llms.txt file valid or invalid?

The check that Google's Lighthouse tooling applies is simple. A file passes when it has an H1 heading, at least one Markdown link, and roughly fifty characters of content. It fails when any of those are missing.

The most common failure is not a missing file. It is a file that exists but contains no links — a paragraph of text about the business and nothing an AI reader can follow. That version passes a human glance and fails the actual check.

Worth knowing: a missing llms.txt is not scored as a failure. Lighthouse marks it "not applicable" rather than counting it against you. A malformed one is the worse outcome, because it looks handled and is not.

What did we find on real business websites?

In August 2026 we ran an agent-readiness scan across 91 live business websites — home services, trades, professional services, hospitality — using Google's own Lighthouse agentic rules.

• 25 of 91 sites had no llms.txt at all. Roughly one in four.
• 6 of the 66 sites that did have one had a malformed file — nearly always the same defect: no Markdown links to key pages.

The second number is the interesting one. Those businesses had already done the work, or someone had done it for them, and the file still would not do its job. Publishing a file is not the same as publishing a useful one.

Does an llms.txt file get you cited by AI?

Not on its own, and anyone promising otherwise is overselling it.

In the same scan we also checked whether AI assistants actually named each business when asked who the best provider in their city was. There was no clean relationship between having a valid llms.txt and being named. Plenty of businesses with a good file were invisible. Plenty without one were named by both ChatGPT and Perplexity.

The honest framing: llms.txt removes an obstacle. It does not create demand. If an AI reader arrives at your site and cannot work out what you do or where your service pages are, the file helps. If nothing is sending AI readers to you in the first place, the file changes nothing — that is a reputation, reviews and citations problem, not a file problem.

How do you publish one?

1. List your genuinely important pages. Services, service areas, about, contact. Not every page — the useful ones.
2. Write it in Markdown. An H1 with your business name, a one-line description, then sections of links.
3. Upload it to your site root so it loads at yoursite.com/llms.txt. Anywhere else and it will not be found.
4. Open it in a browser and confirm it renders as plain text and every link works.
5. Revisit it when your services change. A file pointing at pages you deleted is worse than no file.

Is it worth doing?

It is cheap, it is quick, and the downside is zero. That makes it worth doing — as long as you hold it in proportion. It is site hygiene, in the same bucket as a sitemap or clean heading structure. It is not a growth strategy, and if someone sells it to you as one, ask them what else is in the plan.

The more useful question is the broader one: can an AI agent read and use your site at all? A clean llms.txt sitting on a site where the contact form has unlabelled fields and half the links have no readable text is a tidy map to a building with no door handles. We wrote about that in can AI agents use your website.