What is llms.txt, and do you need one?
Short answer: it is a plain-text contents page for AI tools. It is optional, it is on roughly one site in ten, and a neglected one does more harm than not having one.
The idea
A file at yoursite.com/llms.txt listing your most important pages in plain text, so an AI tool can find what matters without crawling everything and guessing. Think of it as the contents page of a book rather than the index at the back.
What one looks like
> Emergency and scheduled plumbing across Greater Manchester,
> family run since 1998.
## Services
- [Emergency callout](https://acme.example/emergency): 24 hours, one hour response
- [Boiler servicing](https://acme.example/boilers): Annual servicing and repair
## About
- [Coverage area](https://acme.example/areas): Towns and postcodes we cover
- [Pricing](https://acme.example/pricing): Callout charges and hourly rates
That is the whole format. A heading, an optional summary, then sections of links with short descriptions.
Who actually reads it
Honest answer: adoption is real but uneven. Roughly one site in ten now publishes one, including Stripe, Cloudflare and Vercel, and documentation tools like Mintlify have pushed it hard. AI coding assistants use it most reliably. The big search-style assistants treat it as a helpful hint rather than an instruction.
So: worth having, not worth losing sleep over. It costs an hour to write and occasionally saves an AI from summarising you wrongly.
The part people get wrong
This is exactly why we check every link in yours on a schedule rather than validating the file once and calling it done.
Should you bother?
- Documentation or a developer tool? Yes. This is where it genuinely pays off today.
- A business with a handful of service pages? Optional. Get your robots.txt and crawler access right first — those matter far more.
- A large content site? Yes, but keep it current or do not publish it.
Ours is at seensure.com/llms.txt if you want to see a real one.