The LLMS.txt Domain Dilemma: Where Should You Actually Put Your File?

When we first published this post in June 2025, we asked a question that seemed theoretical: if Anthropic keeps its llms.txt at docs.anthropic.com and Shopify keeps one at shopify.dev, what happens to everyone who goes looking for those files on the main domain?

A year later we have answers, and they're better than any hypothetical.

Anthropic moved its entire docs site. The file now lives at platform.claude.com/llms.txt, and the old address only works because they set up a redirect. Shopify retired its developer file without one; shopify.dev/llms.txt returns a 404, every tutorial that linked it points at nothing, and the company's llms.txt now sits at shopify.com/llms.txt. Which is to say: when Shopify rethought its placement, it picked the root of the main domain, the exact spot this post has recommended since day one.

Where you put this file decides whether anyone can find it later. Here's the framework for getting that choice right, whether you run one website or five.

Why major companies split their LLMS.txt files

Companies like Anthropic follow a “content lives where content lives” approach:

• Anthropic's API docs live on their developer platform, so that's where the LLMS.txt goes
• Developer-heavy companies put the file where the developers already are
• From a technical perspective, it's tidy

The catch: there's no standard telling an AI system (or a human) where to look. If someone checks anthropic.com/llms.txt, they hit a dead end, because the file lives on a different domain entirely.

We're still in the phase where the big players experiment and nobody agrees on best practices. Two things have firmed up since 2025, though. Google's Lighthouse audits now check for llms.txt at the root of the domain being tested, so the tools that look for this file look at your main domain. And the August 2026 revision of the llms.txt proposal finally defined how multiple files relate: a file covers the pages under its path, and the most specific file applies. Main domain first, specialized files where the content genuinely lives.

The real-world impact for your business

For most small and medium businesses, this domain confusion is an opportunity. While enterprise companies wrestle with complex subdomain strategies, you can move faster and simpler.

But first, match your setup to your business model.

The four business models and where your LLMS.txt should live

The simple business (most Website HQ clients)

Your situation: one main website, all important content on your primary domain.

Strategy: put your LLMS.txt file at yourdomain.com/llms.txt.

Why this works: it's where visitors, agents, and audit tools all look first, and all your content is there anyway.

Example structure:

yourbusiness.com/llms.txt
- About your services
- Contact information
- Key service pages
- Case studies or testimonials
- Blog highlights

This is the cleanest, most discoverable approach for most businesses.

The course creator with subdomains

Your situation: main business site at yourbusiness.com, courses at learn.yourbusiness.com.

Strategy: a multi-file approach with cross-references.

Why this matters: your courses might be your best offering, and on a subdomain they're invisible to anything that only checks your main domain.

Recommended approach:

• Main domain file (yourbusiness.com/llms.txt): business overview with clear pointers to your course platform
• Course subdomain file (learn.yourbusiness.com/llms.txt): the detailed course catalog
• Cross-link everything: each file references the other

Example main file entry:

## Educational Resources
- [Complete Course Catalog](https://learn.yourbusiness.com): Our training programs
- [Course Documentation](https://learn.yourbusiness.com/llms.txt): Detailed course information for AI systems

The multi-brand business

Your situation: multiple brands or distinct business lines on different domains.

Strategy: separate LLMS.txt files for each brand, with cross-references where the brands publicly connect.

Why this works: each brand speaks with its own voice and stays discoverable.

The complex enterprise (the Anthropic model)

Your situation: corporate site, developer portal, documentation site, community platform.

Strategy: specialized files for each audience, coordinated deliberately.

Why the complexity exists: different audiences need different depth. Just remember what this post opened with: the more domains you spread across, the more moving pieces you own when one of them migrates.

How to decide your domain strategy

Ask yourself 3 questions:

1. Where is your most important content? If your courses, tools, or key resources live on a subdomain, that subdomain needs its own file. Keep your main domain file as the front door that points to it.

2. How do people naturally discover you? Most people (and now Lighthouse) start at yourbusiness.com, so that's where your front-door file belongs, even if it mostly directs traffic elsewhere.

3. What's your growth plan? If you expect to add subdomains or business lines, design the main file so sections can split off later.

The cross-reference strategy that actually works

Your main domain LLMS.txt should include:

## Platform Resources
- [Course Platform](https://learn.yourbusiness.com): Access our complete training library
- [Course Documentation](https://learn.yourbusiness.com/llms.txt): Detailed AI-readable course information
- [Community](https://community.yourbusiness.com): Join our member discussions

Your subdomain LLMS.txt should include:

## About [Your Business Name]
This is the course platform for [Your Business Name]. For complete business information, see yourbusiness.com/llms.txt.

## Available Courses
[Detailed course listings...]

This builds a navigation web that lets an AI system reconstruct your whole operation from any entry point.

The technical implementation

For the single-domain approach (recommended for most businesses):

• Create one LLMS.txt file
• Place it at yourdomain.com/llms.txt
• Include everything important about your business
• Update it whenever you expand to new domains

For the multi-domain approach:

• Start with a hub file on your main domain
• Create specialized files only for subdomains with substantial content
• Cross-reference clearly between files
• Keep your business description consistent across all of them

And one rule the Anthropic migration taught everyone: if a domain ever moves, redirect its llms.txt path along with the pages. Anthropic's old docs URL still lands on the new file because they redirected it. Shopify's old URL lands on a 404. One of those companies gets to keep every link ever pointed at their file.

Build for change

The llms.txt proposal is still settling (its author revised it as recently as August 2026), so design for flexibility:

Start simple. Begin with a single file on your main domain, even if you have subdomains.

Plan for growth. Structure content so you can split it later. Splitting is easy; consolidating scattered files is the painful direction.

Check it quarterly. Load each of your llms.txt URLs and confirm they resolve and still describe reality.

Stay consistent. Describe your business the same way in every file.

What this means for your competitive advantage

While larger companies manage complex domain architectures, smaller businesses can:

• Move faster with simpler, more discoverable implementations
• Put everything in one place instead of coordinating five files
• Adapt quickly as the standard settles

Anthropic needed a migration plan and redirects to move one file. You can update yours in the time it takes to drink a coffee.

Your domain strategy action plan

If you have one main website: put your LLMS.txt at yourdomain.com/llms.txt and include everything important about your business.

If you have courses on a subdomain: create files on both domains with clear cross-references. The main domain file points to the detailed course information.

If you have multiple business lines: separate files for each domain, discoverable from your main brand domain.

If you're planning to expand: design the main file with sections you can later split into subdomain files.

Your domain questions answered

Should I create LLMS.txt files for every subdomain I have?

No. Only create subdomain files where that subdomain has substantial, unique content that matters to your business. A simple blog subdomain can be covered by a few links in your main file.

What happens if I move my site to a new domain?

Redirect the old llms.txt URL to the new one, exactly like you'd redirect your pages. Anthropic is the working example: docs.anthropic.com/llms.txt forwards to platform.claude.com/llms.txt, so every old link still works. Skip the redirect and you get the Shopify outcome, where their old developer-file URL was never forwarded and a year of external links points at a 404.

What if I change my domain structure later?

That's why starting with your main domain makes sense. You can add subdomain files later and update the main file to reference them. Splitting content is much easier than consolidating it.

How do I handle domains I'm planning to retire?

Note the upcoming change in your current file, and when the switch happens, redirect the old domain's llms.txt to your new structure.

Should I copy the same content to multiple domain LLMS.txt files?

Avoid exact duplication. Each file should focus on its own domain's content and cross-reference the rest. Think of a well-organized library system.

What about domains I use just for marketing campaigns?

Skip them. Focus on domains that hold permanent content you want AI systems to understand.

In this series:

1. Why Your Website Needs an LLMS.txt File (And What the Heck That Even Means)
2. What Industry Leaders Put in Their LLMS.txt Files (And How to Steal Their Strategies)
3. How to Create Your First LLMS.txt File: A Step-by-Step Guide
4. The LLMS.txt Domain Dilemma: Where Should You Actually Put Your File? –This article!
5. How to Measure AI Traffic (And Whether Your LLMS.txt File Is Doing Anything at All)