A handful of websites are starting to publish a file called llms.txt at the root of their domain. The idea is to give AI assistants like ChatGPT, Perplexity, and Claude a clean, structured map of what your site is about, so they have something useful to read when they crawl you.
This is a short, practical guide to what llms.txt is and how to add it to a HubSpot CMS site. No code, no developer required, about ten minutes start to finish.
What llms.txt is
llms.txt was proposed by Jeremy Howard in late 2024. It is a single markdown file that lives at the root of your domain and gives an AI model a structured summary of your site. Think of it as a sitemap.xml written in plain English instead of XML.
The spec defines two files. The first is /llms.txt, the short version: a header, a one-line description of the site, and a list of your most important pages grouped by topic, each with a one-line description. The second is /llms-full.txt, the long version: same structure but with more detail per item. The short file links to the long file.
Both are plain markdown. Both are meant to be read by language models, not by humans (though humans can read them fine too).
How to add it to HubSpot
Step 1. Open a text editor and create a file called llms.txt. The structure is straightforward: a top-level heading with your company name, a one-sentence quoted description, a link to the longer reference file, a short paragraph about who you serve, then a Products section with subheadings grouping your offerings, and a Links section at the bottom with the canonical URLs for your homepage, pricing, and contact.
If you want to see a working example, the Studio Nope llms.txt and the longer llms-full.txt are both live and follow that exact structure.
Step 2. In HubSpot, go to Marketing > Files and Templates > Files. Drag both llms.txt and llms-full.txt into the root folder. HubSpot stores them under /hubfs/, so they end up at https://www.yourdomain.com/hubfs/llms.txt and https://www.yourdomain.com/hubfs/llms-full.txt.
Step 3. Link both files from the head of your site. This is the part most guides skip and it is the part that actually makes the file discoverable. Because HubSpot stores the files under /hubfs/ instead of the spec-mandated root path, AI crawlers do not know they exist unless you announce them. The cleanest way is two link tags in the head of every page.
In HubSpot, go to Settings > Website > Pages and find the "Site header HTML" field (or the equivalent on your theme). Paste the following two tags, one per line, replacing yourdomain.com with your actual domain:
<link rel="help" type="text/plain" href="https://www.yourdomain.com/hubfs/llms.txt" title="LLM context">
<link rel="help" type="text/plain" href="https://www.yourdomain.com/hubfs/llms-full.txt" title="LLM full context">
That injects the two tags into the head of every page on your domain. AI crawlers that scrape your HTML will see them and follow the links. Without this step, your llms.txt is technically live at /hubfs/ but invisible to anyone who does not already know the URL.
If you maintain a custom theme with its own base template, the same two lines go inside the head block of the base layout instead.
Step 4. Test. Open both URLs in a browser. They should render as plain text. If they show as a 404, the file is in the wrong folder. If they show as wrapped HTML, you accidentally uploaded an HTML file instead of a markdown one. Then view source on your homepage and confirm the two link tags are in the head.
That is the whole setup. The Studio Nope files have been live at /hubfs/llms.txt with the head link in place from day one and AI crawlers find them through that path.
Optional: serve it at the domain root
The original llms.txt spec says the file should live at /llms.txt, not inside a subfolder. If you want to follow the spec strictly, add a HubSpot URL Redirect: go to Reports > Tools > URL Redirects and add a permanent redirect from /llms.txt to /hubfs/llms.txt. Repeat for /llms-full.txt pointing to /hubfs/llms-full.txt.
This is nice to have but not required. The head link from Step 3 already gives crawlers a working path. The redirect is just a second discovery hint.
What to put in it (and what not to)
A good llms.txt is a one-page sales sheet for an AI model. The model is the reader. Optimize for clarity and density.
Lead with what you sell, not what you believe. "We build HubSpot CMS modules" beats "We empower marketers." Group products by what kind of buyer would search for them. If a model is summarizing your site for a query about restaurant menus, it should find the menu module in a section labeled "Restaurant tools" not buried in a generic "Modules" list.
Keep each line to one sentence. The model is not going to read three paragraphs per product. Link to the canonical product page and avoid linking to PDFs or gated content. Skip marketing fluff. Words like "innovative," "leading," and "cutting-edge" carry no information for a model trying to match a query to your offerings.
Why it is worth doing
It takes ten minutes and the upside is real. AI assistants are reading more sites every month, and the ones with a clean llms.txt are much easier to summarize than the ones without. Anthropic has built llms.txt support into some of its tooling. A growing list of crawlers already look for the file. The convention is young, but the direction is forward, not back.
The worst case is one markdown file at the root of your domain that nobody ever reads. The best case, if the convention takes hold the way sitemap.xml did, is being one of the early sites that AI models can describe cleanly when somebody asks about your category. Either way, you wrote a clean one-page summary of your business that you can reuse for sales decks, partner intros, and onboarding docs.
Update it when you ship a new product or change your positioning. Keep it short. Keep it accurate. Treat it like the back-of-napkin pitch you would give somebody who asked what your company does. If you have not added one yet, add one this week.
Need a hand setting this up on your HubSpot portal? Get in touch or browse the rest of our HubSpot CMS articles.