What Is llms.txt And Why Add One?

llms.txt is a plain text file you place in the root of your website (at yoursite.com/llms.txt) that tells AI engines what your site is about and which pages matter most.

It is similar in concept to robots.txt (which controls which crawlers can access which pages) and sitemap.xml (which lists all your pages for search engines), but it serves a different purpose: it gives AI engines a curated, human written summary of your site so they can understand and cite it more accurately.

Modern websites are messy. They have hundreds of pages, navigation menus, cookie banners, marketing fluff, and content of varying importance. When an AI engine crawls your site, it has to figure out from all that noise what your business actually does and which pages are the authoritative answers to specific questions.

llms.txt fixes that by letting you say it directly. Here is who we are. Here is what we do. Here are the pages that matter. Here is what each one is about.

The result is faster, more accurate AI understanding of your site, which translates into more citations.

The llms.txt format is markdown based and follows a simple convention.

1. Title

Your business name as a level one heading: # Your Business Name

2. Summary

A blockquote summary of your business, what you do, and where you are based. This is the single most important paragraph because AI engines often quote it directly.

3. Sections

Markdown sections (## Section Name) listing your most important pages, each as a markdown link with a short description of what the page is about.

4. Optional content

Contact details, service areas, hours, and any other structured information that helps AI engines understand and represent your business.

Here is a simplified example for a fictional Devon plumber.

# Devon Plumbers Ltd

> Devon Plumbers Ltd is an independent plumbing and heating company based in Newton Abbot, serving Torquay, Paignton, Newton Abbot and the surrounding South Devon area. We specialise in boiler installation, emergency plumbing, bathroom fitting and gas safety inspections.

## Services
- [Boiler Installation](https://example.com/boiler-installation/): New boiler installation across South Devon, with prices from £1,800.
- [Emergency Plumbing](https://example.com/emergency/): 24 hour emergency plumbing across Torbay.
- [Bathroom Installation](https://example.com/bathrooms/): Full bathroom design and fitting service.

## Service Areas
Newton Abbot, Torquay, Paignton, Brixham, Totnes, Teignmouth.

## Contact
- Phone: 01803 123456
- Email: info@example.com
- Address: Example Street, Newton Abbot, Devon TQ12 1AA

llms.txt is a relatively new standard but adoption is growing fast.

• Anthropic (Claude) is one of the strongest backers and treats llms.txt as a primary source of site context.
• Perplexity reads llms.txt files to better understand sites it cites.
• OpenAI (ChatGPT) uses llms.txt as a signal alongside other crawl data.
• Google has not formally endorsed it but is widely believed to be using it as a soft signal.

Even if some engines do not yet use llms.txt heavily, adding one is a low cost, future proofing investment with no downsides.