12 Oct 25 
A plain-English guide to llms.txt, the proposed standard for making your website legible to AI assistants: what it is, what it isn't, how to write one, and whether it's worth your afternoon.
A growing share of your future customers will never see your homepage. They’ll ask an AI assistant “who’s a good agency for X” or “compare tools for Y,” and the assistant will answer from whatever it managed to understand about the web. Which raises a question nobody had to ask before: is your website legible to machines that read on behalf of humans?
That’s the problem llms.txt tries to solve. Here’s the plain-English version.
What It Is
llms.txt is a proposed standard: a single Markdown file at the root of your site (yoursite.com/llms.txt) that gives AI systems a clean, curated summary of who you are and where your important content lives. Think of it as a reception desk for language models. The proposal came from Jeremy Howard of Answer.AI, and the format is deliberately simple: a title, a short description of your business, then organised lists of your key pages with one-line summaries. Full spec at llmstxt.org.
If that sounds familiar, you’re thinking of robots.txt or sitemap.xml. The kinship is real, but the jobs differ. robots.txt tells crawlers what they may not do. A sitemap lists URLs with zero context. llms.txt does the opposite of both: it actively explains your site, in prose a language model can digest in one pass, without fighting through your navigation, cookie banners, and hero animations.
The Honest Caveats
Two things you should know before investing effort. First, llms.txt is a proposal, not a ratified standard. No AI company guarantees they read it. Adoption is a bet, not a certainty. Second, it isn’t magic SEO: it won’t make an AI “rank” you. It just removes friction for any system that does come looking.
So why bother? Because the cost is one afternoon, the downside is zero, and the asymmetry is attractive: if AI assistants continue becoming a discovery channel (and every trend line says they are), the sites that are effortless to understand will get described more accurately, and recommended more confidently, than the sites that are a maze. We’ve added one to our own site on exactly that logic. It’s the same reasoning as structured markup was for search engines years ago: early legibility compounds.
What a Good One Contains
Ours follows a simple recipe you can copy:
- One paragraph of positioning. Who you are, who you serve, what makes you different. Written like you’d brief a smart stranger, not like a tagline.
- Your key pages, grouped and described. Services, case studies, contact, each with a one-line summary that says what a visitor would actually find there.
- Your best content. The blog posts and resources that demonstrate expertise, again with honest one-liners, not keyword soup.
- Practical facts machines get wrong. Minimum engagement, locations served, contact email. The things an assistant would otherwise guess.
Two anti-patterns to avoid: don’t dump your entire sitemap in (curation is the whole point), and don’t write marketing fluff (a model summarising fluff produces fluff about you; write facts).
Should You Have One?
Our rule of thumb: if your business gets found through research (people comparing options, asking for recommendations, evaluating expertise), yes, spend the afternoon. Service businesses, SaaS, consultancies, anyone with a considered purchase cycle. If you’re a pure impulse-purchase storefront, it matters less today.
It’s rare that future-proofing costs this little. One Markdown file, one afternoon, and your site has a reception desk for the fastest-growing kind of visitor: the one reading on someone else’s behalf.
Want yours written and structured properly, along with the rest of your site’s machine-legibility? We do this as part of our web work.