llms.txt and Content-Signal: the new files for AI visibility

Why AI sees your site differently

The Google bot crawls pages and builds an index from them. AI answer systems, by contrast, fetch individual pages at runtime, read the text and summarise it. Nested menus, a lot of JavaScript and unstructured pages make that hard for them. The clearer your content is, the more likely it gets understood correctly and cited.

What llms.txt is

llms.txt is a simple text file in the root directory of your domain (so your-domain.com/llms.txt). It works like a short table of contents for AI systems: who you are, what you offer and which pages are the important ones. In Markdown, easy to read, without ballast.

# Sample Roofing Ltd
> Master roofing business in Lüneburg and the surrounding area.

## Services
- Roof renovation: /services/roof-renovation
- Maintenance and repair: /services/maintenance

## Contact
- Address, phone, opening hours: /contact

That way an AI system finds the core information without having to work through your whole site. It is a young standard, not used by everyone yet, but the effort is minimal.

Content-Signal in robots.txt

You may already know robots.txt, it controls what search engines are allowed to crawl. What is new is the Content-Signal directive: with it you tell AI systems how your content may be used. One line is enough:

Content-Signal: ai-train=yes, search=yes, ai-retrieval=yes

That explicitly allows your content to be used for AI search and AI answers, which is exactly what you want if you would like to show up in ChatGPT and Perplexity. It is also important not to block AI crawlers by accident (through a Cloudflare rule, for example), because otherwise even the best llms.txt cannot do anything.

The order of importance

So that the expectation is right: these files are the finishing touch, not the foundation. Work on AI visibility pays off in this order:

• Citable, clearly structured content with concrete answers, numbers and prices.
• Clean schema (Organization, LocalBusiness, Person) and consistent contact details.
• Do not block access for AI crawlers.
• Then llms.txt and Content-Signal as an additional, clean signal.