# llms.txt and llms-full.txt

> Fern automatically creates llms.txt files for AI developer tools. Filter by language, control visibility, and track analytics for LLM traffic.

[llms.txt](https://llmstxt.org/) is a standard for exposing website content to AI developer tools. Fern implements this standard, automatically generating and maintaining `llms.txt` and `llms-full.txt` Markdown files for your documentation site. When an LLM bot accesses your docs, Fern serves these Markdown files instead of HTML, reducing token consumption by 90%+.

<Frame>
  <img src="https://files.buildwithfern.com/fern.docs.buildwithfern.com/learn/1c185b18406eca1fab6e4bb38b78cccf02f4eb6de5fbb5f179230f1ccd600730/products/docs/pages/ai/llms-txt.png" alt="Example of using llms.txt" />
</Frame>

## Generated files

Fern generates two files for LLMs:

* **`llms.txt`** contains a lightweight summary of your documentation site with each page distilled into a one-sentence description and URL.

* **`llms-full.txt`** contains complete documentation content including the full text of all pages. For API documentation, this includes your complete API Reference with resolved OpenAPI specifications and SDK code examples for enabled languages.

Both files are available at any level of your documentation hierarchy (`/llms.txt`, `/llms-full.txt`, `/docs/llms.txt`, `/docs/ai-features/llms-full.txt`, etc.).

Examples: [Eleven Labs llms.txt](https://elevenlabs.io/docs/creative-platform/voices/llms.txt), [Cash App llms-full.txt](https://developers.cash.app/llms-full.txt).

### Page descriptions

Both files include page descriptions pulled from [frontmatter](/learn/docs/configuration/page-level-settings). Fern uses the `description` field if present, otherwise falls back to `subtitle`.

```mdx title="Frontmatter"
---
title: Fern Docs
subtitle: Build beautiful documentation websites with Fern.
---
```

The output format depends on whether you're requesting an individual page or a section:

**Individual page** — Both `llms.txt` and `llms-full.txt` return the same format:

```txt title=".../page/llms.txt and .../page/llms-full.txt"