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# llms.txt Format, Spec Reference

The complete reference for the llms.txt file format: required and optional elements, Markdown rules, link syntax, the llms-full.txt variant, and a checklist to validate your file.

Last updated: August 12, 2026

## Format overview

`llms.txt` is a plain-text resource using [CommonMark Markdown](https://commonmark.org/). It may live at the origin root or a
more specific path such as `https://example.com/docs/llms.txt`. The most specific
applicable file describes that scope.

Compatible coding assistants, RAG pipelines and research agents can use the file as a curated
map. Publication alone does not prove discovery or use, so declare it with `rel="describedby"`
where appropriate and measure the clients you actually support.

## Required elements

The August 2026 proposal defines one mandatory element:

- **H1 heading**, the first line must be an H1 (`# Name`) containing the
project or site name.   
The blockquote summary, explanatory preamble, H2 file lists and link notes are optional.
Minimal valid llms.txt   
Copy

```
# Your Project Name

> One sentence describing what your project does and who it's for.

## Documentation

- [Getting Started](https://example.com/docs/start): Install and first steps.
- [API Reference](https://example.com/api): Full endpoint catalog.

## Optional

- [Changelog](https://example.com/changelog): Release history.

```

## Optional sections

Sections are H2 headings (`##`) followed by unordered lists of Markdown links. Common
section names include:

- **Documentation**, primary docs, guides, references. 
- **Product**, marketing pages, pricing, status. 
- **Examples**, code samples, tutorials, demos. 
- **Optional**, changelog, blog, GitHub, lower priority for AI. 
- **API**, dedicated API reference section. 
- **SDKs**, language-specific client libraries.   
**Optional** remains a clear editorial label for secondary resources, but v2 assigns
it no special processing semantics.
Full example llms.txt   
Copy

```
# Acme SaaS

> Acme SaaS helps teams automate their billing workflows with a no-code dashboard
> and a REST API supporting 40+ payment providers.

## Product

- [Overview](https://acme.com/product): Core capabilities and use cases.
- [Pricing](https://acme.com/pricing): Plans, limits, and enterprise options.
- [Status](https://status.acme.com/): Uptime and incident history.

## Documentation

- [Quickstart](https://acme.com/docs/quickstart): Set up in under 5 minutes.
- [API Reference](https://acme.com/docs/api): REST endpoints, auth, rate limits.
- [SDKs](https://acme.com/docs/sdks): Node, Python, Ruby, Go clients.
- [Webhooks](https://acme.com/docs/webhooks): Event payloads and retry policy.

## Examples

- [Node.js integration](https://acme.com/examples/node): End-to-end payment flow.
- [Python integration](https://acme.com/examples/python): Subscription management.

## Optional

- [Changelog](https://acme.com/changelog): Version history.
- [Blog](https://acme.com/blog): Product updates and tutorials.
- [GitHub](https://github.com/acme/acme-oss): Open-source components.

```

## Link syntax

Each link follows the Markdown syntax `- [Title](URL): short description.`

- Use **absolute URLs** including the scheme (`https://`). 
- The description after the colon is plain text, keep it under ~120 characters and make it
informative for an AI, not keyword-stuffed. 
- One link per list item, do not nest bullets. 
- Prefer canonical URLs (with trailing slash if that's your convention).     
✓ Write descriptions for AI readers

Unlike HTML alt text or SEO meta descriptions, the link descriptions in  llms.txt  are read by language models building a mental map of your project. Be precise:
"Full REST endpoint catalog with auth and rate-limit details" is more useful than "API docs".

## llms-full.txt variant

The wider ecosystem uses an optional companion file at `/llms-full.txt`. While `llms.txt` is an index of links, `llms-full.txt` contains the *full text* of those linked pages concatenated together,
formatted in Markdown.

A tool that explicitly supports the convention may fetch `llms-full.txt` for consolidated
context. The trade-off is greater size, staleness and security exposure.

Read the dedicated [llms-full.txt guide](/llms-full-txt/) for generation strategies.

## Checklist

- File served at the root or the intended scoped path 
- Plain-text or Markdown media type with UTF-8 encoding 
- Starts with exactly one H1 heading 
- Optional blockquote and preamble contain no headings 
- Link targets resolve correctly in their publication context 
- Optional link notes are concise and factual 
- File size is justified by the tasks and tested clients 
- No HTML tags, no nested lists 
- Validated with the [llms.txt validator](/validator/)   
## Common mistakes

- **Relative URLs**, `- [Docs](/docs)` will not resolve correctly when the
file is fetched by an AI crawler. Always use absolute URLs. 
- **Missing blockquote**, skipping the `> summary` makes the file harder
for models to parse and is non-compliant with the spec. 
- **Wrong Content-Type**, serving with `text/html` or no content-type causes
some parsers to reject the file. 
- **Keyword stuffing descriptions**, AI models read these literally. Stuffing
keywords degrades the quality signal. 
- **Listing every page**, curate your most important 10–30 links. An exhaustive
sitemap belongs in `llms-full.txt`, not the index.   
## Related guides

- [How to create llms.txt](/how-to-create/), step-by-step for any stack. 
- [llms-full.txt guide](/llms-full-txt/), full-content companion file. 
- [Validator](/validator/), check your file for spec compliance. 
- [Generator](/generator/), create a file from a form. 
- [Best practices](/best-practices/), what to include and what to skip. 
- [Which AI crawlers read llms.txt](/llms-txt-ai-crawlers/), adoption status.        
## Sources

- [ llmstxt.org, official spec ](https://llmstxt.org/)
- [ Answer.AI, original proposal ](https://www.answer.ai/posts/2024-09-03-llmstxt.html)           
On this page

- [ Format overview ](#overview)
- [ Required elements ](#required)
- [ Optional sections ](#sections)
- [ Link syntax ](#links)
- [ llms-full.txt variant ](#llms-full)
- [ Checklist ](#checklist)
- [ Common mistakes ](#mistakes)